fix(supermemory): honor auto capture across lifecycle flushes

[CryptoKylan]

Summary

Fixes an auto_capture: false policy leak in the bundled Supermemory provider.

sync_turn() already obeyed this setting, but three independent automatic lifecycle flushes bypassed it:

• gateway transcript ingestion through on_session_end() (including compaction/session boundaries),
• buffered-turn flushing through on_session_switch(), and
• the process-termination fallback flush.

All three now honor the same policy. Explicit user-intent writes through supermemory_store and on_memory_write() remain available when automatic capture is disabled.

Follow-up to #21690 / #21692. Replaces #78617, which became stuck on a stale fork head after a reviewed amendment.

Independent review

The final diff was independently reviewed by provenance-verified claude-opus-5 (high confidence; pass_with_watchlist, no blocking defects). One state bookkeeping issue found during the first review was repaired with a failing regression before the second review.

Validation

python -m pytest tests/plugins/memory/test_supermemory_autocapture_guard.py tests/plugins/memory/test_supermemory_provider.py -o 'addopts=' -q\n34 passed\n\nruff check plugins/memory/supermemory/__init__.py tests/plugins/memory/test_supermemory_autocapture_guard.py\nAll checks passed!\n\npython -m py_compile plugins/memory/supermemory/__init__.py\ngit diff --check\n```

[alt-glitch]

This was generated by AI during triage.

@Dhravya @MaheshtheDev Tagging you on this Supermemory provider item as the soft maintainers.

[CryptoKylan]

Refreshed onto current main (33f8e96a72) with authorship and the single-commit shape preserved.

Current validation:

• full memory-plugin suite: 293 passed
• Ruff: passed
• py_compile: passed
• git diff --check: passed

GitHub now reports the refreshed head 8aebbb7ce7 as mergeable.