feat(transcription): dismiss + keyboard-operate the re-edit dropdown (#628 AC-4/AC-9)

Adds a visible × dismiss control to MentionDropdown (shared by the fresh-@ and
re-edit paths) and, for the re-edit path which has no Tiptap suggestion plugin
to forward keys, focuses the search input on open and handles its own keyboard:
Escape dismisses (AC-4), Arrow/Enter reuse the exported selection logic so the
dropdown is navigable on its own (AC-9 parity with the fresh-@ dropdown).

Both close paths (Escape + ×) leave the mention node attrs + text byte-identical
(AC-4) — close() never touches the document. Controller wires ondismiss=close
(+refocus editor) and focusOnMount only for the re-edit open.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/lib/shared/discussion/MentionDropdown.svelte

@@ -2,7 +2,7 @@
 import type { components } from '$lib/generated/api';
 // eslint-disable-next-line boundaries/dependencies -- mention dropdown needs person date formatting; extract to shared if it becomes reusable
 import { formatLifeDateRange } from '$lib/person/personLifeDates';
-import { untrack } from 'svelte';
+import { onMount, untrack } from 'svelte';
 import { m } from '$lib/paraglide/messages.js';
 // Layered defence cap on the @mention search query length (CWE-400
 // amplification). The <input maxlength> attribute below caps direct
@@ -31,17 +31,42 @@ type DropdownState = {
 let {
 	model,
 	editorQuery = '',
-	onSearch = () => {}
+	onSearch = () => {},
+	ondismiss = () => {},
+	focusOnMount = false
 }: {
 	model: DropdownState;
 	/** Text typed after `@` in the host editor. Mirrors into the search input
 	 *  until the user takes manual ownership by typing into the input itself. */
 	editorQuery?: string;
 	onSearch?: (query: string) => void;
+	/** Closes the dropdown without touching the document — invoked by the visible
+	 *  × dismiss control and by Escape on the re-edit path (#628 AC-4). */
+	ondismiss?: () => void;
+	/** Re-edit (#628) opens with the search field focused; the fresh-@ path keeps
+	 *  focus in the editor so typing flows to the contenteditable. */
+	focusOnMount?: boolean;
 } = $props();
 
 let searchQuery = $state(untrack(() => editorQuery.slice(0, MAX_QUERY_LENGTH)));
 let userHasEdited = $state(false);
+let searchInput: HTMLInputElement;
+
+onMount(() => {
+	if (focusOnMount) searchInput?.focus();
+});
+
+// Re-edit has no Tiptap suggestion plugin to forward keys, so the search input
+// handles its own navigation: Escape dismisses (and is prevented from clearing
+// the native search field), Arrow/Enter reuse the exported selection logic.
+function handleSearchKeydown(event: KeyboardEvent) {
+	if (event.key === 'Escape') {
+		event.preventDefault();
+		ondismiss();
+		return;
+	}
+	if (onKeyDown(event)) event.preventDefault();
+}
 
 // Intent-revealing alias used by both the persistent aria-live announcer and
 // the visible empty-state copy. Folding the duplicated rule into one $derived
@@ -184,6 +209,7 @@ function selectItem(item: Person) {
 				<path d="m20 20-3.5-3.5" stroke-linecap="round" />
 			</svg>
 			<input
+				bind:this={searchInput}
 				id="mention-search"
 				type="search"
 				data-test-search-input
@@ -194,8 +220,34 @@ function selectItem(item: Person) {
 				oninput={() => {
 					userHasEdited = true;
 				}}
+				onkeydown={handleSearchKeydown}
 				onmousedown={(e) => e.stopPropagation()}
 			/>
+			<!--
+				Visible dismiss control (#628 AC-4) — shared by the fresh-@ and the
+				re-edit paths. onmousedown preventDefault keeps the editor selection
+				from blurring before onclick fires; onclick handles both pointer and
+				keyboard (Enter/Space) activation.
+			-->
+			<button
+				type="button"
+				data-test-dismiss
+				aria-label={m.person_mention_dismiss_label()}
+				class="inline-flex h-11 w-11 shrink-0 items-center justify-center rounded-sm text-ink-2 hover:bg-canvas focus:bg-canvas focus-visible:ring-2 focus-visible:ring-brand-navy focus-visible:outline-none focus-visible:ring-inset"
+				onmousedown={(e) => e.preventDefault()}
+				onclick={() => ondismiss()}
+			>
+				<svg
+					aria-hidden="true"
+					viewBox="0 0 24 24"
+					fill="none"
+					stroke="currentColor"
+					stroke-width="2"
+					class="h-5 w-5"
+				>
+					<path d="M6 6l12 12M18 6 6 18" stroke-linecap="round" />
+				</svg>
+			</button>
 		</div>
 	</div>
 	<!--

frontend/src/lib/shared/discussion/PersonMentionEditor.svelte

@@ -82,8 +82,10 @@ type LooseRenderProps = {
 // and (#628) the pencil re-edit affordance — so at most one dropdown is ever
 // mounted (the AC-6 single-dropdown invariant). open() closes any prior
 // dropdown first; render() is a thin adapter over open()/update()/close().
+type OpenOptions = { focusOnMount?: boolean };
+
 type MentionController = {
-	open: (clientRect: RectGetter, query: string, commit: CommitFn) => void;
+	open: (clientRect: RectGetter, query: string, commit: CommitFn, opts?: OpenOptions) => void;
 	update: (clientRect: RectGetter, query: string, commit: CommitFn) => void;
 	close: () => void;
 	onKeyDown: (event: KeyboardEvent) => boolean;
@@ -155,7 +157,19 @@ function createMentionController(): MentionController {
 		dropdownState.editorQuery = query.slice(0, MAX_QUERY_LENGTH);
 	};
 
-	const open = (clientRect: RectGetter, query: string, commit: CommitFn) => {
+	// Close the dropdown without touching the document and return focus to the
+	// editor — wired to the dropdown's × control and the re-edit Escape path.
+	const dismiss = () => {
+		close();
+		editor?.commands.focus();
+	};
+
+	const open = (
+		clientRect: RectGetter,
+		query: string,
+		commit: CommitFn,
+		opts: OpenOptions = {}
+	) => {
 		// Single-dropdown invariant: tear down any open dropdown before mounting a
 		// new one, and bump the request token so a previous open's in-flight fetch
 		// cannot repopulate this dropdown.
@@ -167,6 +181,8 @@ function createMentionController(): MentionController {
 			target: document.body,
 			props: {
 				model: dropdownState,
+				ondismiss: dismiss,
+				focusOnMount: opts.focusOnMount ?? false,
 				// MentionDropdown reads `editorQuery` off the shared state proxy via
 				// this getter — Svelte 5's mount() does not expose settable prop
 				// accessors, so we route through the proxy (same pattern as items).
@@ -219,7 +235,7 @@ function commitRelink(pos: number): CommitFn {
 // the stored displayName.
 function requestRelink(getRect: () => DOMRect | null, displayName: string, pos: number) {
 	if (!editor || !editor.isEditable) return;
-	controller.open(getRect, displayName, commitRelink(pos));
+	controller.open(getRect, displayName, commitRelink(pos), { focusOnMount: true });
 }
 
 onMount(() => {

frontend/src/lib/shared/discussion/PersonMentionEditor.svelte.spec.ts

@@ -957,4 +957,93 @@ describe('PersonMentionEditor — #628 re-edit pencil', () => {
 			expect(host.snapshot.value).not.toContain('@Anna');
 		});
 	});
+
+	// AC-4 — dismiss leaves the node byte-identical on BOTH close paths ---------
+
+	function dismissButton() {
+		return page.getByRole('button', { name: m.person_mention_dismiss_label() });
+	}
+
+	it('AC-4: Escape closes the re-edit dropdown leaving the node byte-identical', async () => {
+		mockFetchWithPersons();
+		const host = await renderSavedMention();
+		clickPencil(await pencilElement());
+		await vi.waitFor(async () => {
+			await expect.element(page.getByRole('searchbox')).toBeVisible();
+		});
+
+		const search = (await page.getByRole('searchbox').element()) as HTMLElement;
+		search.dispatchEvent(
+			new KeyboardEvent('keydown', { key: 'Escape', bubbles: true, cancelable: true })
+		);
+
+		await vi.waitFor(async () => {
+			await expect.element(page.getByRole('listbox')).not.toBeInTheDocument();
+		});
+		expect(host.snapshot.value).toBe('@Aug ');
+		expect(host.snapshot.mentionedPersons).toEqual([{ personId: 'p-aug', displayName: 'Aug' }]);
+	});
+
+	it('AC-4: the visible dismiss control closes the re-edit dropdown leaving the node byte-identical', async () => {
+		mockFetchWithPersons();
+		const host = await renderSavedMention();
+		clickPencil(await pencilElement());
+		await expect.element(dismissButton()).toBeVisible();
+
+		const dismissEl = (await dismissButton().element()) as HTMLElement;
+		dismissEl.dispatchEvent(new MouseEvent('click', { bubbles: true, cancelable: true }));
+
+		await vi.waitFor(async () => {
+			await expect.element(page.getByRole('listbox')).not.toBeInTheDocument();
+		});
+		expect(host.snapshot.value).toBe('@Aug ');
+		expect(host.snapshot.mentionedPersons).toEqual([{ personId: 'p-aug', displayName: 'Aug' }]);
+	});
+
+	// AC-9 parity — the re-edit dropdown is keyboard-operable on its own --------
+
+	it('re-edit open focuses the search input so keyboard users land in the field', async () => {
+		mockFetchEmpty();
+		await renderSavedMention();
+		clickPencil(await pencilElement());
+		await vi.waitFor(async () => {
+			await expect.element(page.getByRole('searchbox')).toBeVisible();
+		});
+
+		const search = (await page.getByRole('searchbox').element()) as HTMLElement;
+		await vi.waitFor(() => {
+			expect(document.activeElement).toBe(search);
+		});
+	});
+
+	it('re-edit dropdown is keyboard-navigable: ArrowDown then Enter relinks', async () => {
+		mockFetchWithPersons(); // [AUGUSTE (p-aug, highlighted), ANNA (p-anna)]
+		const host = await renderSavedMention();
+		clickPencil(await pencilElement());
+		await vi.waitFor(async () => {
+			await expect.element(page.getByRole('option', { name: /Anna Schmidt/ })).toBeVisible();
+		});
+
+		const search = (await page.getByRole('searchbox').element()) as HTMLElement;
+		search.dispatchEvent(
+			new KeyboardEvent('keydown', { key: 'ArrowDown', bubbles: true, cancelable: true })
+		);
+		search.dispatchEvent(
+			new KeyboardEvent('keydown', { key: 'Enter', bubbles: true, cancelable: true })
+		);
+
+		await vi.waitFor(() => {
+			expect(host.snapshot.mentionedPersons[0].personId).toBe('p-anna');
+			expect(host.snapshot.mentionedPersons[0].displayName).toBe('Aug');
+		});
+	});
+
+	// The × control is shared with the fresh-@ dropdown ------------------------
+
+	it('the fresh-@ dropdown also exposes the shared dismiss control', async () => {
+		mockFetchWithPersons();
+		renderHost();
+		await userEvent.type(page.getByRole('textbox'), '@Aug');
+		await expect.element(dismissButton()).toBeVisible();
+	});
 });