Fix: Always release search index writer, even on failure, so the write lock doesn't persist for later (#12865)

src/documents/search/_backend.py

@@ -225,12 +225,14 @@ class WriteBatch:
                 # in-progress merge on the same index files.
                 self._writer.wait_merging_threads()
                 self._backend._index.reload()
-            # Explicitly delete writer to release tantivy's internal lock.
-            # On exception the uncommitted writer is simply discarded.
+        finally:
+            # Always release the writer (and Tantivy's internal writer lock),
+            # even if commit/merge/reload raised, so the next batch can acquire
+            # a writer instead of failing with LockBusy. An uncommitted writer
+            # is simply discarded.
             if self._raw_writer is not None:
                 del self._raw_writer
                 self._raw_writer = None
-        finally:
             if self._lock is not None:
                 self._lock.release()