Add updateDocument() helper to store.ts

Add new helper function to update document hash and title simultaneously.
This is useful when file content changes but the path stays the same.

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Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

store.ts

@@ -1101,6 +1101,21 @@ export function updateDocumentTitle(
     .run(title, modifiedAt, documentId);
 }
 
+/**
+ * Update an existing document's hash, title, and modified_at timestamp.
+ * Used when content changes but the file path stays the same.
+ */
+export function updateDocument(
+  db: Database,
+  documentId: number,
+  title: string,
+  hash: string,
+  modifiedAt: string
+): void {
+  db.prepare(`UPDATE documents SET title = ?, hash = ?, modified_at = ? WHERE id = ?`)
+    .run(title, hash, modifiedAt, documentId);
+}
+
 /**
  * Deactivate a document (mark as inactive but don't delete).
  */