Phase 2c review follow-up on the id()-reuse persistence fix:
- test_recycled_id_in_dedup_set_still_persists_new_message seeded an EMPTY
dedup set, so it never injected a collision and passed under id-based dedup
too (couldn't distinguish the designs). Replace with
test_stale_seed_id_from_prior_flush_cannot_suppress_new_message, which asserts
the durable invariant: the seed is empty after every flush (mutation-checked:
removing the post-flush reset now fails BOTH id-reuse tests).
- Refresh the _flush_messages_to_session_db docstring: it still described the
old per-session identity tracking; document the intrinsic-marker mechanism,
that _flushed_db_message_ids is now a one-shot seed, and the shared-dict
mutation safety note.
kshitijk4poor
d3010b74db