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/BulkDocumentEditLayout.svelte

@@ -134,6 +134,16 @@ async function handleDiscard() {
 		});
 		if (!ok) return;
 	}
+	if (mode === 'edit') {
+		// In edit mode the file map IS the user's bulk selection — discarding
+		// must clear the upstream store and bounce back to the list, otherwise
+		// the user is left on /documents/bulk-edit with an empty form and a
+		// stale count in the bottom bar (issue #225 Bulk-Edit Panel table).
+		bulkSelectionStore.clear();
+		discardAll();
+		await goto('/documents');
+		return;
+	}
 	discardAll();
 }