feat(vector): index files in real time on vector-index tag changes

Tagging an existing file/folder emits only OCP\SystemTag\MapperEvent — never a
Node*Event — so tagged PDFs were previously only picked up by the hourly
scanner. Subscribe to the tag event and reconcile membership so adding/removing
the `vector-index` tag (re)indexes in near-real time.

- webhook_presets: add OCP\SystemTag\MapperEvent to the files_sync preset
  (NC 32+, where MapperEvent gained getWebhookSerializable(); harmless on older
  servers — it just never fires).
- webhook_parser: parse MapperEvent (objectType=files) into a path-less file
  "reconcile" task. The payload carries only a fileid + tagIds (no name/path),
  so assign and unassign both collapse to a reconcile.
- processor._reconcile_tag_event: resolve the fileid against the user's current
  vector-index PDFs (find_files_by_tag). Present -> index with the resolved
  path/etag; absent -> flip to delete. Naturally handles "an unrelated tag
  changed" and a tagged folder's own fileid (no-op; the scanner still expands
  folders to descendants).
- Unit tests for the parser branch and the reconcile.

The matching admin-UI preset change ships separately in the astrolabe app repo.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/unit/test_webhook_presets.py

@@ -89,6 +89,18 @@ def test_get_deck_preset():
     assert "OCA\\Deck\\Event\\BoardUpdatedEvent" in event_classes
 
 
+@pytest.mark.unit
+def test_files_sync_includes_systemtag_event():
+    """files_sync registers the SystemTag MapperEvent so tag changes (NC 32+)
+    drive vector-index (re)indexing, alongside the node create/write/delete
+    events."""
+    preset = get_preset("files_sync")
+    assert preset is not None
+    event_classes = [e["event"] for e in preset["events"]]
+    assert "OCP\\SystemTag\\MapperEvent" in event_classes
+    assert "OCP\\Files\\Events\\Node\\NodeCreatedEvent" in event_classes
+
+
 @pytest.mark.unit
 def test_filter_presets_subset_installed():
     """Test filtering when only some apps are installed."""