refactor(search): address PR #750 round 11 review feedback

Three minor fixes from the round-11 review on PR #750:

- bm25_hybrid.py:209 — Comment said `doc_id` is `int (notes) or str (files)`,
  which is backwards. Notes, news_items, and deck_cards are stored as `str`
  (scanner.py:241, 666, 867); files are stored as `int` (scanner.py:425).
  Updated to point readers at scanner.py as the source of truth.

- verification.py:338 — Lowered the News-API 403/404 log line from `info`
  to `debug`. The News app being uninstalled or disabled is a predictable
  operational state (matching the other verifiers' debug-on-not-found
  paths), so this should not generate operator-dashboard noise. Transient
  errors immediately below stay at `warning` because they're unexpected.

- semantic.py:809 — `nc_get_vector_sync_status` was reading
  `document_receive_stream` via `getattr(..., None)`, but the attribute is
  guaranteed-defined on both `AppContext` and `OAuthAppContext` (as a
  field with `None` default). The defensive `getattr` masked typos that
  the eviction_task_group access at semantic.py:197-199 deliberately
  surfaces. Switched to direct access; the `if … is None:` value-check
  below is preserved (the attribute can legitimately be None before sync
  starts).

Items deliberately deferred (with rationale in the plan file):
- News verifier semaphore-hold during get_items (reviewer: "not required
  here, just worth tracking"; ADR already lists follow-ups).
- Hardcoded 2× over-fetch / VERIFICATION_OVERFETCH (TODO already in code).
- Integration test for the real Qdrant eviction filter (reviewer marked
  low-priority; type-preservation chain is unit-tested).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

nextcloud_mcp_server/search/bm25_hybrid.py

@@ -208,7 +208,7 @@ class BM25HybridSearchAlgorithm(SearchAlgorithm):
             for result in search_response.points:
                 if result.payload is None:
                     continue
-                # doc_id can be int (notes) or str (files - file paths)
+                # doc_id can be int (files) or str (notes/news_items/deck_cards) — see scanner.py
                 doc_id = result.payload["doc_id"]
                 doc_type = result.payload.get("doc_type", "note")
                 chunk_start = result.payload.get("chunk_start_offset")