Preserve turnsUsed on crash and signal finalizers

[TheGreatAxios]

Summary

• Crash and signal finalizers copy turnsUsed from the in-memory active-run handle instead of writing 0
• Persist snapshots keep that handle in step so a signaled run with N persisted turns writes turnsUsed: N

Verification

• bun run typecheck and bun run build pass
• Focused tests for this change pass (12/12: active-run, session-start crash guard, crash/signal/exec-signal finalize)
• bun run check hits 4 pre-existing failures unrelated to this change (createOptimizedContextStore torn-tail/hook, assembleChatAgent EROFS)

Fixes CL-7644

[linear-code]

CL-7644

[TheGreatAxios]

Review · Comment

Crash and signal finalizers copy run.turnsUsed from the in-memory handle instead of hardcoding 0.

Findings

• src/tui/runner/exit.ts:596 — /new//clear repoints activeRunHandle.sessionId then awaits initSessionDir / buildAgent before the new running persist. A crash in that window writes the outgoing session’s turnsUsed onto the new session. Previously this path wrote 0, which is correct for a fresh session.

Notes

• Mid-run persist syncs the handle before the first await. Exec-signal integration already prefers handle over disk.

[TheGreatAxios]

Critic · Comment

Handle stays in step with persist on the primary mid-run path. Rotation is the hole.

Findings

• src/tui/runner/exit.ts:596 — crash after rotation sessionId reassignment and before the new running snapshot mixes live new sessionId with outgoing turnsUsed. simulate-crash.ts leaves turnsUsed: 3 after repoint; rotation integration does not assert the count.