feat: use Nextcloud filename for indexed file title + reconcile on rename

The vector-sync pipeline derived an indexed file's display title from the
document's embedded metadata (e.g. a PDF's /Title), falling back to the
filename only when absent. That embedded title frequently disagrees with how
the user named the file in Nextcloud and is confusing in the astrolabe
vector-viz UI (a passive consumer of the `title` payload field).

For files, always derive the title from the Nextcloud filename via a shared
`file_title_from_path` helper. Notes/deck/news keep their metadata titles.

A rename/move in Nextcloud keeps the fileid (doc_id) and content (etag/mtime)
but changes the path, so both the dedup claim and the scanner freshness gate
skip re-embedding and the stored file_path/title go stale. Add
`reconcile_document_path`: a metadata-only set_payload that refreshes
file_path + title on the existing real chunks without re-fetch/re-embed.
Wire it into both skip paths:
  - dedup hit (etag unchanged on rename) via claim_existing_index(current_path=...)
  - scanner incremental skip (etag changed, mtime stable)
Both reuse already-fetched payloads, so steady-state scans add no extra
round-trip (reconcile is a no-op when the path is unchanged).

Refs: Deck #204

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

nextcloud_mcp_server/vector/scanner.py

@@ -32,7 +32,10 @@ from nextcloud_mcp_server.vector.placeholder import (
 )
 from nextcloud_mcp_server.vector.qdrant_client import get_qdrant_client
 from nextcloud_mcp_server.vector.queue.ports import TaskProducer
-from nextcloud_mcp_server.vector.sharing_state import claim_existing_index
+from nextcloud_mcp_server.vector.sharing_state import (
+    claim_existing_index,
+    reconcile_document_path,
+)
 
 logger = logging.getLogger(__name__)
 
@@ -466,7 +469,9 @@ async def scan_user_documents(
                 # it. Eliminates the per-user reprocessing ping-pong that arises
                 # because chunk point IDs are user-agnostic (note 386945 #5).
                 etag = str(file_info.get("etag") or "")
-                if etag and await claim_existing_index(file_id, "file", etag, user_id):
+                if etag and await claim_existing_index(
+                    file_id, "file", etag, user_id, current_path=file_path
+                ):
                     _potentially_deleted.pop((user_id, file_id), None)
                     logger.debug(
                         "Dedup: file %s (ID: %s) already indexed in tenant; "
@@ -582,6 +587,28 @@ async def scan_user_documents(
                             )
                         )
                         file_queued += 1
+                    elif existing_metadata is not None:
+                        # Unchanged content (not re-queued) but the file may have
+                        # been renamed/moved: a rename keeps the fileid while
+                        # changing the path, and the dedup miss here means the
+                        # etag changed without a modified_at bump. Refresh the
+                        # stale path/title metadata without re-embedding. No-op
+                        # when the path is unchanged.
+                        try:
+                            await reconcile_document_path(
+                                file_id,
+                                "file",
+                                existing_metadata.get("file_path"),
+                                file_path,
+                            )
+                        except Exception as exc:  # noqa: BLE001 — non-fatal
+                            logger.warning(
+                                "Path reconcile failed for file %s (ID: %s) (%s); "
+                                "next scan retries",
+                                file_path,
+                                file_id,
+                                exc,
+                            )
 
             logger.info(
                 "[SCAN-%s] Found %s tagged PDFs for %s", scan_id, file_count, user_id