fix: prevent duplicate turn uploads

[johnbuccola]

Problem

The Stop hook uploads a trailing in-progress turn without recording it in the sidecar. A later hook uploads the completed turn under a new trace ID, which duplicates usage. Concurrent Stop hooks can also race past the sidecar.

Fix

• wait until a turn has a task_complete or turn_aborted event
• serialize top-level uploads per rollout with a short-lived atomic lock
• recover locks older than the hook timeout

Explicitly interrupted turns remain eligible because turn_aborted marks them completed.

Verification

• 39 tests pass
• formatting and TypeScript checks pass
• committed bundle reproduces cleanly

[claude]

Claude Code Review

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[CLAassistant]

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