* fix(entity_resolver): prevent _pending_stats/_pending_cooccurrences memory leak
Add discard_pending_stats() to EntityResolver to clean up both pending dicts
for the current task key. Call it at the start of each _run_db_work attempt so
that exceptions between accumulation and flush_pending_stats() — including
deadlock retries — never leave stale entries keyed by recycled task IDs.
Fixes#660
* test(entity_resolver): add unit tests for discard_pending_stats()
Covers: clears both dicts for current task, is idempotent when empty,
and does not touch entries belonging to other task keys.
No database required — purely in-memory logic.
e6333719ee