fix(sync): fence post-merge audio finalization

[Git-on-my-level]

Summary

• Exclude a lifecycle-fenced merged conversation from updated_memories after deferred reprocessing loses ownership.
• Preserve processing and audio finalization for unaffected sibling conversations.
• Prevent the later private-cloud audio finalizer from writing audio_files, precache state, or an artifact job for a fenced conversation.

Failure class

Failure-Class: FC-split-mutation-authority

Verification

• BACKEND_UNIT_TEST_FILE_LIST=/tmp/omi-10234-fenced-finalization-tests.txt bash backend/test.sh -- -k merged_reprocess_fence_isolated_to_its_conversation -vv — 164 passed.
• The regression first failed before the production change: the fenced ID remained in updated_memories; after the fix it proves only the current sibling reaches audio finalization.

Risk

Low. The change removes post-fence side effects only for the conversation whose lifecycle ownership was explicitly lost. It does not change the fence itself, retry/terminal semantics, or the sibling-success path.

Closes #10234

[chatgpt-codex-connector]

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[Git-on-my-level]

@codex review

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 1082f6f9c6

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[Git-on-my-level]

Addressed Codex review feedback (discussion_r3628593415): a fenced conversation ID that appeared in both new_memories and updated_memories was only discarded from updated_memories, leaving it in new_memories. Since _finalize_sync_audio_files unions both buckets, the fenced conversation still received audio/precache/artifact side effects.

Fix: discard fenced IDs from new_memories in both the fence handler (_reprocess_merged_conversations) and the retry-hydration path. Updated the unit tests to cover the dual-bucket scenario and the retry path.

Also repaired two rebase casualties: restored reportUnusedImport=false on the pipeline pyright comment and updated the e2e stub for the new on_fenced parameter.

[Git-on-my-level]

Monitor pass: resolved Codex thread on _reprocess_merged_conversations fence persistence (discussion_r3628072595). The fence is already durably checkpointed to both the content ledger and job partial result via _checkpoint_fenced_conversations_for_run before audio finalization, and retry hydration unions the tombstone and filters stale IDs from updated_memories/new_memories — the concern was fully addressed in the existing code.

Backend unit suite remains red, but the 3 failing files (test_desktop_transcribe.py, test_smoke_what_matters_now.py, test_workflow_contracts.py) fail identically on upstream main (571ece3) and are unrelated to this PR's sync pipeline changes.

[kodjima33]

fix(sync): fence post-merge audio finalization, closes #10234, regression test proves fix, CI green — 5/5