Separate translator checkpoints from finalization

[Stephen Belanger (Qard)]

What this changes

A delivery flush and a session shutdown are different lifecycle events. Previously both called the same translator flush method, so an ordinary delivery barrier could close the live session root, turn, and pending work. Later events then reused state that had already been finalized.

This PR gives that distinction one shared daemon contract:

• checkpoint catches up externally buffered observations and flushes the sink without ending the logical session
• finalize runs only when the session actor shuts down or is retired
• Codex catches up transcript rows in both paths but closes dangling work only during finalization
• Claude Code, Antigravity, OpenCode, and Pi keep state across checkpoints and defensively close incomplete work during finalization
• Pi and OpenCode now preserve interrupted LLM/tool spans as explicit errored spans instead of silently dropping them

This is the translator-lifecycle slice extracted from #26. It deliberately does not include source identity, managed-run, import, or distribution changes.

Current-main and overlap check

Rebuilt directly on current main at c29184b. The open PRs were reviewed before publishing: #28 concerns JavaScript span transforms, #33 removes MCP proxy packages, and #26 is the omnibus being replaced. None implements this lifecycle separation.

Validation

• cargo fmt --manifest-path bt-daemon/Cargo.toml -- --check
• cargo clippy --manifest-path bt-daemon/Cargo.toml --all-targets --all-features -- -D warnings
• cargo test --manifest-path bt-daemon/Cargo.toml --all-features

The four real-agent tests remain ignored because they require installed agent CLIs and credentials; all deterministic tests pass.

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-01T14:19:24.152048Z	6c9c548	PR opened

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Reviewed commit: 6c9c5482dc

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