Hitting Stop (globalPause) disposed the AI merge agent session but left
the spawned `pnpm test` / `pnpm build` child processes running until
they finished naturally. With recurring flaky-test loops at Step 5,
that meant Stop had no visible effect — new test runs kept piling up
across multiple worktrees.
Two gaps:
- project-engine.ts onGlobalPause never called mergeAbortController.abort(),
so subsequent verification commands (gated by the signal) weren't cancelled.
- merger.ts execWithProcessGroup only listened to its own internal
timeout — passing an AbortSignal had no effect on the in-flight
child process group.
Fix: abort the controller on global pause, and have execWithProcessGroup
SIGTERM/SIGKILL the detached process group when its signal aborts.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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