fix(vector-sync): address round-5 review — partial-failure signal, markers

- purge route: include a "failed" key in the 200 body listing requested doc
  types that were not purged, so Astrolabe knows consent isn't yet enforced
  for them (scanner backstop still catches up)
- tests: add @pytest.mark.unit / module-level pytestmark to the new test
  modules so they run under `pytest -m unit`; add a partial-failure route test
- capabilities: comment why the cache is keyed per-user despite a global value
- semantic/scanner: doc/comment clarifications (sorted-order, eviction timing)

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

tests/unit/vector/test_purge.py

@@ -10,6 +10,8 @@ import pytest
 import nextcloud_mcp_server.vector.purge as purge_module
 from nextcloud_mcp_server.vector.purge import purge_doc_types
 
+pytestmark = pytest.mark.unit
+
 
 def _patch_qdrant(monkeypatch, *, counts: dict[str, int], delete_raises=None):
     """Wire a fake Qdrant client whose ``count`` reflects ``counts`` per

tests/unit/vector/test_scanner_consent_backstop.py

@@ -18,6 +18,8 @@ from nextcloud_mcp_server.vector import scanner as scanner_module
 from nextcloud_mcp_server.vector.queue.ports import TaskProducer
 from nextcloud_mcp_server.vector.scanner import _enqueue_deletes_for_disabled_types
 
+pytestmark = pytest.mark.unit
+
 
 @pytest.fixture(autouse=True)
 def _clear_backstop_state():