refactor(search): address PR #750 review feedback

- Cap all_results to limit*2 after sort in the per-doc_types branch of
  nc_semantic_search to bound over-verification (was unbounded N-types).
- Switch BatchVerifier from (client, doc_ids, user_id) to (client, results,
  semaphore). Verifiers now read file paths and deck board/stack ids from
  SearchResult.metadata instead of doing fresh Qdrant scrolls — eliminates
  one duplicate round-trip per file/deck-card verification.
- Bound per-id verification concurrency with a shared anyio.Semaphore
  (default 20, matching server/semantic.py context-expansion convention).
  Prevents httpx pool exhaustion / rate limiting on large search pages.
- Propagate stack_id from Qdrant payload to SearchResult.metadata in both
  bm25_hybrid.py and semantic.py (board_id was already propagated).
- Drop now-unused _resolve_file_path / _resolve_deck_metadata helpers.
- Drop redundant int(d) in requested predicate from _verify_news_items.
- Rewrite eviction comment to be honest about inline (not background)
  execution and the resulting latency coupling.
- ADR-019 status: Proposed -> Accepted.
- Add news property to NextcloudClientProtocol.
- Widen SearchResult.id and SemanticSearchResult.id to int | str to match
  BatchVerifier signature and document support for future string-id types.
- Flip openWorldHint to True on nc_semantic_search_answer (it calls into
  Nextcloud via nc_semantic_search).

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

nextcloud_mcp_server/models/semantic.py

@@ -10,7 +10,13 @@ from .base import BaseResponse
 class SemanticSearchResult(BaseModel):
     """Model for semantic search results with additional metadata."""
 
-    id: int = Field(description="Document ID (int for all document types)")
+    id: int | str = Field(
+        description=(
+            "Document ID. Numeric for all currently indexed types (notes, files, "
+            "deck cards, news items); typed as int|str to allow future doc types "
+            "that use string identifiers."
+        )
+    )
     doc_type: str = Field(
         description="Document type (note, calendar_event, deck_card, etc.)"
     )