fix(document-detail): force edit panel on notification deep-link

Comments only render inside TranscriptionEditView, so a deep-link
into a document with existing reviewed transcriptions landed the
user in read mode with no comment element in the DOM — the scroll
target silently missed.

scrollToCommentFromQuery now takes a setPanelMode callback and calls
it with 'edit' whenever both query params are present. The page's
own transcribe-mode $effect checks a skipInitialPanelMode flag the
deep-link flow sets, so its default-panel-mode logic doesn't race
against the explicit override.

Two new helper tests pin the contract: panel mode is forced to
'edit' both when transcribe mode is off (entering fresh) and when
it is already on (same-page notification click).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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

@@ -40,6 +40,10 @@ let activeAnnotationId = $state<string | null>(null);
 let highlightBlockId = $state<string | null>(null);
 let flashAnnotationId = $state<string | null>(null);
 let pdfStripExpanded = $state(false);
+// Flag set by the deep-link helper so the transcribe-mode $effect does not
+// overwrite the panelMode it picked (e.g. forcing 'edit' on notification
+// click-through). One-shot: consumed after the effect's loadBlocks resolves.
+let skipInitialPanelMode = $state(false);
 
 const prefersReducedMotion = $derived(
 	typeof window !== 'undefined' && window.matchMedia('(prefers-reduced-motion: reduce)').matches
@@ -281,7 +285,11 @@ async function checkOcrStatus() {
 $effect(() => {
 	if (transcribeMode) {
 		loadTranscriptionBlocks().then(() => {
-			panelMode = transcriptionBlocks.length > 0 ? 'read' : 'edit';
+			if (skipInitialPanelMode) {
+				skipInitialPanelMode = false;
+			} else {
+				panelMode = transcriptionBlocks.length > 0 ? 'read' : 'edit';
+			}
 		});
 		checkOcrStatus();
 	}
@@ -309,6 +317,10 @@ onMount(() => {
 	scrollToCommentFromQuery(new URL(page.url), {
 		transcribeMode,
 		setTranscribeMode: (v) => (transcribeMode = v),
+		setPanelMode: (m) => {
+			skipInitialPanelMode = true;
+			panelMode = m;
+		},
 		loadBlocks: loadTranscriptionBlocks,
 		setActiveAnnotationId: (id) => (activeAnnotationId = id),
 		flashAnnotation: (annotationId) => {