refactor(types): extract shared types to \$lib/types.ts

Eliminates type duplication across 6 files by introducing a single
shared types module:

- Comment + CommentReply: were identically defined in CommentThread,
  PanelDiscussion, and DocumentBottomPanel
- DocumentPanelTab: was identically defined in DocumentBottomPanel
  and documents/[id]/+page.svelte
- Annotation: was defined in both AnnotationLayer and PdfViewer
  (PdfViewer's variant with fileHash? is now the canonical definition)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/components/AnnotationLayer.svelte

@@ -1,15 +1,5 @@
 <script lang="ts">
-type Annotation = {
-	id: string;
-	documentId: string;
-	pageNumber: number;
-	x: number;
-	y: number;
-	width: number;
-	height: number;
-	color: string;
-	createdAt: string;
-};
+import type { Annotation } from '$lib/types';
 
 type DrawRect = {
 	x: number;

frontend/src/lib/components/CommentThread.svelte

@@ -1,25 +1,7 @@
 <script lang="ts">
 import { onMount, untrack } from 'svelte';
 import { m } from '$lib/paraglide/messages.js';
-
-type CommentReply = {
-	id: string;
-	authorId: string | null;
-	authorName: string;
-	content: string;
-	createdAt: string;
-	updatedAt: string;
-};
-
-type Comment = {
-	id: string;
-	authorId: string | null;
-	authorName: string;
-	content: string;
-	createdAt: string;
-	updatedAt: string;
-	replies: CommentReply[];
-};
+import type { Comment, CommentReply } from '$lib/types';
 
 type Props = {
 	documentId: string;
@@ -189,154 +171,95 @@ onMount(() => {
 });
 </script>
 
+<!--
+  Renders a single comment or reply entry.
+  showReplyButton: whether the "Reply" button appears (only on last item in a thread).
+-->
+{#snippet commentEntry(comment: Comment | CommentReply, threadId: string, showReplyButton: boolean)}
+	{#if editingId === comment.id}
+		<div class="flex flex-col gap-2">
+			<textarea
+				class="w-full resize-none rounded border border-line px-3 py-2 font-serif text-sm text-ink focus:ring-1 focus:ring-accent focus:outline-none"
+				rows={3}
+				bind:value={editText}
+			></textarea>
+			<div class="flex items-center gap-3">
+				<button
+					class="rounded bg-primary px-3 py-1.5 font-sans text-xs font-medium text-white hover:bg-primary/80 disabled:opacity-40"
+					disabled={posting}
+					onclick={() => saveEdit(comment.id)}
+				>
+					{m.btn_save()}
+				</button>
+				<button
+					class="font-sans text-xs text-ink-3 transition-colors hover:text-ink"
+					onclick={cancelEdit}
+				>
+					{m.btn_cancel()}
+				</button>
+			</div>
+		</div>
+	{:else}
+		<div class="flex items-start justify-between gap-2">
+			<div class="min-w-0 flex-1">
+				<div class="flex flex-wrap items-center gap-2">
+					<span class="font-sans text-xs font-semibold text-ink">{comment.authorName}</span>
+					<span class="font-sans text-xs text-ink-3">{timeAgo(comment.createdAt)}</span>
+					{#if wasEdited(comment)}
+						<span class="font-sans text-xs text-ink-3">
+							{m.comment_edited_label()}
+							{timeAgo(comment.updatedAt)}
+						</span>
+					{/if}
+				</div>
+				<p class="mt-1 font-serif text-sm leading-relaxed text-ink-2">{comment.content}</p>
+			</div>
+			{#if canModify(comment)}
+				<div class="flex shrink-0 items-center gap-2">
+					<button
+						class="font-sans text-xs text-ink-3 transition-colors hover:text-ink"
+						onclick={() => startEdit(comment)}
+					>
+						{m.btn_edit()}
+					</button>
+					<button
+						class="font-sans text-xs text-ink-3 transition-colors hover:text-ink"
+						onclick={() => deleteComment(comment.id)}
+					>
+						{m.btn_delete()}
+					</button>
+				</div>
+			{/if}
+		</div>
+		{#if showReplyButton && canComment}
+			<div class="mt-1">
+				<button
+					class="font-sans text-xs font-medium text-accent transition-colors hover:text-ink"
+					onclick={() => startReply(threadId)}
+				>
+					{m.comment_btn_reply()}
+				</button>
+			</div>
+		{/if}
+	{/if}
+{/snippet}
+
 <div class="space-y-4">
 	{#each comments as thread, ti (thread.id)}
 		<div class={ti > 0 ? 'border-t border-line pt-4' : ''}>
 			<!-- Root comment -->
 			<div>
-				{#if editingId === thread.id}
-					<div class="flex flex-col gap-2">
-						<textarea
-							class="w-full resize-none rounded border border-line px-3 py-2 font-serif text-sm text-ink focus:ring-1 focus:ring-accent focus:outline-none"
-							rows={3}
-							bind:value={editText}
-						></textarea>
-						<div class="flex items-center gap-3">
-							<button
-								class="rounded bg-primary px-3 py-1.5 font-sans text-xs font-medium text-white hover:bg-primary/80 disabled:opacity-40"
-								disabled={posting}
-								onclick={() => saveEdit(thread.id)}
-							>
-								{m.btn_save()}
-							</button>
-							<button
-								class="font-sans text-xs text-ink-3 transition-colors hover:text-ink"
-								onclick={cancelEdit}
-							>
-								{m.btn_cancel()}
-							</button>
-						</div>
-					</div>
-				{:else}
-					<div class="flex items-start justify-between gap-2">
-						<div class="min-w-0 flex-1">
-							<div class="flex flex-wrap items-center gap-2">
-								<span class="font-sans text-xs font-semibold text-ink">{thread.authorName}</span>
-								<span class="font-sans text-xs text-ink-3">{timeAgo(thread.createdAt)}</span>
-								{#if wasEdited(thread)}
-									<span class="font-sans text-xs text-ink-3">
-										{m.comment_edited_label()}
-										{timeAgo(thread.updatedAt)}
-									</span>
-								{/if}
-							</div>
-							<p class="mt-1 font-serif text-sm leading-relaxed text-ink-2">{thread.content}</p>
-						</div>
-						{#if canModify(thread)}
-							<div class="flex shrink-0 items-center gap-2">
-								<button
-									class="font-sans text-xs text-ink-3 transition-colors hover:text-ink"
-									onclick={() => startEdit(thread)}
-								>
-									{m.btn_edit()}
-								</button>
-								<button
-									class="font-sans text-xs text-ink-3 transition-colors hover:text-ink"
-									onclick={() => deleteComment(thread.id)}
-								>
-									{m.btn_delete()}
-								</button>
-							</div>
-						{/if}
-					</div>
-					<!-- Reply button on root comment only if there are no replies -->
-					{#if thread.replies.length === 0 && canComment}
-						<div class="mt-1">
-							<button
-								class="font-sans text-xs font-medium text-accent transition-colors hover:text-ink"
-								onclick={() => startReply(thread.id)}
-							>
-								{m.comment_btn_reply()}
-							</button>
-						</div>
-					{/if}
-				{/if}
+				{@render commentEntry(thread, thread.id, thread.replies.length === 0)}
 			</div>
 
 			<!-- Replies -->
 			{#each thread.replies as reply, ri (reply.id)}
 				<div class="mt-3 ml-6 border-l-2 border-line pl-4">
-					{#if editingId === reply.id}
-						<div class="flex flex-col gap-2">
-							<textarea
-								class="w-full resize-none rounded border border-line px-3 py-2 font-serif text-sm text-ink focus:ring-1 focus:ring-accent focus:outline-none"
-								rows={3}
-								bind:value={editText}
-							></textarea>
-							<div class="flex items-center gap-3">
-								<button
-									class="rounded bg-primary px-3 py-1.5 font-sans text-xs font-medium text-white hover:bg-primary/80 disabled:opacity-40"
-									disabled={posting}
-									onclick={() => saveEdit(reply.id)}
-								>
-									{m.btn_save()}
-								</button>
-								<button
-									class="font-sans text-xs text-ink-3 transition-colors hover:text-ink"
-									onclick={cancelEdit}
-								>
-									{m.btn_cancel()}
-								</button>
-							</div>
-						</div>
-					{:else}
-						<div class="flex items-start justify-between gap-2">
-							<div class="min-w-0 flex-1">
-								<div class="flex flex-wrap items-center gap-2">
-									<span class="font-sans text-xs font-semibold text-ink">{reply.authorName}</span>
-									<span class="font-sans text-xs text-ink-3">{timeAgo(reply.createdAt)}</span>
-									{#if wasEdited(reply)}
-										<span class="font-sans text-xs text-ink-3">
-											{m.comment_edited_label()}
-											{timeAgo(reply.updatedAt)}
-										</span>
-									{/if}
-								</div>
-								<p class="mt-1 font-serif text-sm leading-relaxed text-ink-2">{reply.content}</p>
-							</div>
-							{#if canModify(reply)}
-								<div class="flex shrink-0 items-center gap-2">
-									<button
-										class="font-sans text-xs text-ink-3 transition-colors hover:text-ink"
-										onclick={() => startEdit(reply)}
-									>
-										{m.btn_edit()}
-									</button>
-									<button
-										class="font-sans text-xs text-ink-3 transition-colors hover:text-ink"
-										onclick={() => deleteComment(reply.id)}
-									>
-										{m.btn_delete()}
-									</button>
-								</div>
-							{/if}
-						</div>
-						<!-- Reply button only on the last reply -->
-						{#if ri === thread.replies.length - 1 && canComment}
-							<div class="mt-1">
-								<button
-									class="font-sans text-xs font-medium text-accent transition-colors hover:text-ink"
-									onclick={() => startReply(thread.id)}
-								>
-									{m.comment_btn_reply()}
-								</button>
-							</div>
-						{/if}
-					{/if}
+					{@render commentEntry(reply, thread.id, ri === thread.replies.length - 1)}
 				</div>
 			{/each}
 
-			<!-- Reply textarea (shown when replyingTo === thread.id) -->
+			<!-- Reply compose box -->
 			{#if replyingTo === thread.id}
 				<div class="mt-3 ml-6 flex flex-col gap-2">
 					<textarea
@@ -365,7 +288,7 @@ onMount(() => {
 		</div>
 	{/each}
 
-	<!-- New top-level comment textarea -->
+	<!-- New top-level comment -->
 	{#if canComment}
 		<div class={comments.length > 0 ? 'border-t border-line pt-4' : ''}>
 			<div class="flex flex-col gap-2">

frontend/src/lib/components/DocumentBottomPanel.svelte

@@ -4,27 +4,7 @@ import PanelMetadata from './PanelMetadata.svelte';
 import PanelTranscription from './PanelTranscription.svelte';
 import PanelDiscussion from './PanelDiscussion.svelte';
 import PanelHistory from './PanelHistory.svelte';
-
-type Tab = 'metadata' | 'transcription' | 'discussion' | 'history';
-
-type CommentReply = {
-	id: string;
-	authorId: string | null;
-	authorName: string;
-	content: string;
-	createdAt: string;
-	updatedAt: string;
-};
-
-type Comment = {
-	id: string;
-	authorId: string | null;
-	authorName: string;
-	content: string;
-	createdAt: string;
-	updatedAt: string;
-	replies: CommentReply[];
-};
+import type { Comment, DocumentPanelTab } from '$lib/types';
 
 type Doc = {
 	id: string;
@@ -47,7 +27,7 @@ type Props = {
 	canAdmin: boolean;
 	open: boolean;
 	height: number;
-	activeTab: Tab;
+	activeTab: DocumentPanelTab;
 };
 
 let {
@@ -72,7 +52,7 @@ function fullHeight() {
 	return window.innerHeight - (topbar?.getBoundingClientRect().bottom ?? 0);
 }
 
-function openTab(tab: Tab) {
+function openTab(tab: DocumentPanelTab) {
 	activeTab = tab;
 	if (!open) {
 		open = true;
@@ -110,7 +90,7 @@ function onDragEnd() {
 	isDragging = false;
 }
 
-const tabs: { id: Tab; label: () => string }[] = [
+const tabs: { id: DocumentPanelTab; label: () => string }[] = [
 	{ id: 'metadata', label: m.doc_panel_tab_metadata },
 	{ id: 'transcription', label: m.doc_panel_tab_transcription },
 	{ id: 'discussion', label: m.doc_panel_tab_discussion },

frontend/src/lib/components/PanelDiscussion.svelte

@@ -1,24 +1,6 @@
 <script lang="ts">
 import CommentThread from './CommentThread.svelte';
-
-type CommentReply = {
-	id: string;
-	authorId: string | null;
-	authorName: string;
-	content: string;
-	createdAt: string;
-	updatedAt: string;
-};
-
-type Comment = {
-	id: string;
-	authorId: string | null;
-	authorName: string;
-	content: string;
-	createdAt: string;
-	updatedAt: string;
-	replies: CommentReply[];
-};
+import type { Comment } from '$lib/types';
 
 type Props = {
 	documentId: string;

frontend/src/lib/components/PdfViewer.svelte

@@ -3,6 +3,7 @@ import { onMount } from 'svelte';
 import { SvelteMap } from 'svelte/reactivity';
 import type { PDFDocumentProxy, PDFPageProxy, RenderTask } from 'pdfjs-dist';
 import AnnotationLayer from './AnnotationLayer.svelte';
+import type { Annotation } from '$lib/types';
 import { m } from '$lib/paraglide/messages.js';
 
 let {
@@ -43,19 +44,6 @@ let textLayerInstance: { cancel: () => void } | null = null;
 let pdfjsLib: typeof import('pdfjs-dist') | null = null;
 let pdfjsReady = $state(false);
 
-type Annotation = {
-	id: string;
-	documentId: string;
-	pageNumber: number;
-	x: number;
-	y: number;
-	width: number;
-	height: number;
-	color: string;
-	createdAt: string;
-	fileHash?: string | null;
-};
-
 let annotations = $state<Annotation[]>([]);
 let annotateColor = $state('#ffff00');
 let commentCounts = new SvelteMap<string, number>();

frontend/src/lib/types.ts

@@ -0,0 +1,33 @@
+export type CommentReply = {
+	id: string;
+	authorId: string | null;
+	authorName: string;
+	content: string;
+	createdAt: string;
+	updatedAt: string;
+};
+
+export type Comment = {
+	id: string;
+	authorId: string | null;
+	authorName: string;
+	content: string;
+	createdAt: string;
+	updatedAt: string;
+	replies: CommentReply[];
+};
+
+export type DocumentPanelTab = 'metadata' | 'transcription' | 'discussion' | 'history';
+
+export type Annotation = {
+	id: string;
+	documentId: string;
+	pageNumber: number;
+	x: number;
+	y: number;
+	width: number;
+	height: number;
+	color: string;
+	createdAt: string;
+	fileHash?: string | null;
+};

frontend/src/routes/documents/[id]/+page.svelte

@@ -4,8 +4,7 @@ import DocumentTopBar from '$lib/components/DocumentTopBar.svelte';
 import DocumentViewer from '$lib/components/DocumentViewer.svelte';
 import DocumentBottomPanel from '$lib/components/DocumentBottomPanel.svelte';
 import AnnotationSidePanel from '$lib/components/AnnotationSidePanel.svelte';
-
-type Tab = 'metadata' | 'transcription' | 'discussion' | 'history';
+import type { DocumentPanelTab } from '$lib/types';
 
 let { data } = $props();
 
@@ -72,7 +71,7 @@ const LS_KEY_TAB = 'doc-panel-tab';
 let panelOpen = $state(false);
 let panelHeight = $state(0); // set to full height on mount
 let navHeight = $state(0);
-let activeTab = $state<Tab>('metadata');
+let activeTab = $state<DocumentPanelTab>('metadata');
 let localStorageRestored = $state(false);
 
 onMount(() => {
@@ -82,7 +81,7 @@ onMount(() => {
 	const savedTab = localStorage.getItem(LS_KEY_TAB);
 
 	if (savedTab && ['metadata', 'transcription', 'discussion', 'history'].includes(savedTab)) {
-		activeTab = savedTab as Tab;
+		activeTab = savedTab as DocumentPanelTab;
 	}
 	const topbar = document.querySelector('[data-topbar]');
 	panelHeight = window.innerHeight - navHeight - (topbar?.getBoundingClientRect().height ?? 0);