fix(bulk-edit): drop dead initial-* props and clear store on edit-mode discard

Felix B1 — `WhoWhenSection.svelte:37` and `DescriptionSection.svelte:42`
mutated $bindable props at top-level script scope, seeding them from
`initial*` companion props that no caller ever passes. The pattern stomps
parent-owned state in any future component re-evaluation.

Removed the dead initialDateIso / initialLocation / initialDocumentLocation
props and let the bindables carry their own initial value. dateDisplay and
currentTitle now seed from the bindable directly inside untrack — no
re-assignment required.

Elicit B2 — In edit mode the file map IS the user's bulk selection, so
discarding must clear bulkSelectionStore and bounce back to /documents,
otherwise the user is left on /documents/bulk-edit with an empty form
and a stale count in the bottom bar.

Refs #225, PR #331

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

frontend/src/lib/components/document/DescriptionSection.svelte

@@ -11,7 +11,6 @@ let {
 	archiveBox = $bindable(''),
 	archiveFolder = $bindable(''),
 	initialTitle = '',
-	initialDocumentLocation = '',
 	initialSummary = '',
 	titleRequired = false,
 	suggestedTitle = '',
@@ -24,7 +23,6 @@ let {
 	archiveBox?: string;
 	archiveFolder?: string;
 	initialTitle?: string;
-	initialDocumentLocation?: string;
 	initialSummary?: string;
 	titleRequired?: boolean;
 	suggestedTitle?: string;
@@ -32,14 +30,11 @@ let {
 	editMode?: boolean;
 } = $props();
 
+// currentTitle seeds from initialTitle once at mount; subsequent edits flow
+// through the oninput handler that flips titleDirty.
 let titleDirty = $state(false);
 currentTitle = untrack(() => initialTitle);
 const titleValue = $derived(titleDirty ? currentTitle : suggestedTitle || currentTitle);
-
-// Initialize controlled location field once from the legacy initial-* props so
-// callers that haven't switched to the bindable form keep their existing
-// pre-fill behaviour.
-documentLocation = untrack(() => documentLocation || initialDocumentLocation);
 </script>
 
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