refactor: address PR #851 review round 5 (ingest transport)

- _clear_vector_sync_state also nulls shutdown_event / scanner_wake_event on
  shutdown, symmetric with the stream/producer fields (the next startup rebinds
  them via _wire_vector_sync_state).
- Comment that the "DocumentTask" string subscript in LocalTransport is
  intentional (TYPE_CHECKING-only class; anyio ignores the runtime type arg).
- Move app.py's annotation-only IngestTransport / TaskProducer imports under
  TYPE_CHECKING (the module uses `from __future__ import annotations`), keeping
  only build_transport at runtime.

Refs: Deck #196

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

nextcloud_mcp_server/app.py

@@ -9,7 +9,7 @@ import traceback
 from collections.abc import AsyncIterator
 from contextlib import AsyncExitStack, asynccontextmanager
 from dataclasses import dataclass
-from typing import Any, cast
+from typing import TYPE_CHECKING, Any, cast
 from urllib.parse import urlparse
 
 import anyio
@@ -133,14 +133,15 @@ from nextcloud_mcp_server.vector.oauth_sync import (
 from nextcloud_mcp_server.vector.placeholder import sweep_orphan_placeholders
 from nextcloud_mcp_server.vector.processor import processor_task
 from nextcloud_mcp_server.vector.qdrant_client import get_qdrant_client
-from nextcloud_mcp_server.vector.queue import (
+from nextcloud_mcp_server.vector.queue import build_transport
-    IngestTransport,
-    TaskProducer,
-    build_transport,
-)
 from nextcloud_mcp_server.vector.scanner import scanner_task
 from nextcloud_mcp_server.vector.webhook_receiver import handle_nextcloud_webhook
 
+if TYPE_CHECKING:
+    # Annotation-only in this module (the file uses `from __future__ import
+    # annotations`, so these are never evaluated at runtime).
+    from nextcloud_mcp_server.vector.queue import IngestTransport, TaskProducer
+
 logger = logging.getLogger(__name__)
 HTTPXClientInstrumentor().instrument()
 
@@ -405,6 +406,10 @@ def _clear_vector_sync_state() -> None:
     _vector_sync_state.task_producer = None
     _vector_sync_state.document_send_stream = None
     _vector_sync_state.document_receive_stream = None
+    # Symmetric with the fields above: the just-fired events belong to the
+    # closed lifespan; the next startup's _wire_vector_sync_state rebinds them.
+    _vector_sync_state.shutdown_event = None
+    _vector_sync_state.scanner_wake_event = None
 
 
 @dataclass

nextcloud_mcp_server/vector/queue/transport.py

@@ -153,6 +153,9 @@ class LocalTransport(IngestTransport):
     """
 
     def __init__(self, max_buffer_size: float):
+        # "DocumentTask" as a string (not the symbol): the class is
+        # TYPE_CHECKING-only here, and anyio ignores the runtime value of the
+        # type argument — so the string is intentional, not a typo.
         send_stream, receive_stream = anyio.create_memory_object_stream["DocumentTask"](
             max_buffer_size=max_buffer_size
         )