- _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>
