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/vector/test_tag_reconcile.py

@@ -0,0 +1,87 @@
+"""Unit tests for processor._reconcile_tag_event.
+
+A SystemTag MapperEvent enqueues a file task with only a fileid (file_path is
+None). The reconcile resolves the file's *current* ``vector-index`` membership
+and mutates the task into a concrete index (path/etag filled) or a delete.
+"""
+
+from unittest.mock import AsyncMock, MagicMock
+
+import pytest
+
+from nextcloud_mcp_server.vector.processor import _reconcile_tag_event
+from nextcloud_mcp_server.vector.scanner import DocumentTask
+
+
+def _tag_task(doc_id: str = "478087") -> DocumentTask:
+    return DocumentTask(
+        user_id="alice",
+        doc_id=doc_id,
+        doc_type="file",
+        operation="index",
+        modified_at=0,
+        file_path=None,
+    )
+
+
+@pytest.mark.unit
+async def test_reconcile_tagged_file_becomes_index():
+    """A fileid still carrying the tag is resolved to a concrete index task."""
+    nc_client = MagicMock()
+    nc_client.find_files_by_tag = AsyncMock(
+        return_value=[
+            {
+                "id": "478087",
+                "path": "/alice/files/Docs/report.pdf",
+                "etag": "abc123",
+                "last_modified_timestamp": 1762850245,
+            }
+        ]
+    )
+
+    task = _tag_task("478087")
+    await _reconcile_tag_event(task, nc_client)
+
+    assert task.operation == "index"
+    assert task.file_path == "/alice/files/Docs/report.pdf"
+    assert task.etag == "abc123"
+    assert task.modified_at == 1762850245
+    nc_client.find_files_by_tag.assert_awaited_once_with(
+        "vector-index", mime_type_filter="application/pdf"
+    )
+
+
+@pytest.mark.unit
+async def test_reconcile_untagged_file_becomes_delete():
+    """A fileid absent from the tagged set flips the task to a delete."""
+    nc_client = MagicMock()
+    nc_client.find_files_by_tag = AsyncMock(
+        return_value=[
+            {"id": "999", "path": "/alice/files/other.pdf", "etag": "z"},
+        ]
+    )
+
+    task = _tag_task("478087")
+    await _reconcile_tag_event(task, nc_client)
+
+    assert task.operation == "delete"
+    # Path stays None — the delete path addresses points by doc_id only.
+    assert task.file_path is None
+
+
+@pytest.mark.unit
+async def test_reconcile_preserves_existing_etag():
+    """An etag already on the task is not overwritten by the tag listing."""
+    nc_client = MagicMock()
+    nc_client.find_files_by_tag = AsyncMock(
+        return_value=[
+            {"id": "478087", "path": "/alice/files/r.pdf", "etag": "from-listing"}
+        ]
+    )
+
+    task = _tag_task("478087")
+    task.etag = "preset"
+    await _reconcile_tag_event(task, nc_client)
+
+    assert task.etag == "preset"
+    assert task.file_path == "/alice/files/r.pdf"