fix(codexexec): ensure context cancellation reliably terminates spawned codex process

[activadee]

Summary

• Propagate context cancellation from codexexec.Runner.Run to callers.
• Prefer returning ctx.Err on cancellation over wrapped read/wait errors.
• Ensure the spawned codex process terminates reliably when the context is canceled.

Details

• Map scanner/read and cmd.Wait() cancellation cases to context.Canceled/context.DeadlineExceeded as appropriate.
• When ctx is canceled, return ctx.Err() even if read/wait surfaced a different error due to process teardown.
• Keeps stderr buffering and exit-code reporting behavior for genuine failures.

Tests

• Add thread_cancel_test.go: integration test that cancels a streaming run and asserts:
  • Wait() returns context.Canceled
  • The spawned process exits
• Add internal/codexexec/testdata/fakecodex: a tiny fake codex binary that writes its PID and blocks until receiving SIGINT/SIGTERM.
• Skip on Windows since the test relies on Unix signals.

Notes

• No public API changes; error behavior on cancellation is now consistent and predictable.
  closes Correctness: reliable context cancellation tears down CLI process #13

[github-actions]

Codex Review Summary

Recommendation: ✅ Ready to merge – no blocking issues detected.

Summary:
Reviewed the updated cancellation handling in internal/codexexec/runner.go along with the new fake Codex helper and integration test; the context error propagation now aligns with the caller’s expectations and the test convincingly verifies the child process is terminated. I don’t see any correctness, stability, or maintainability issues in this PR.

Inline findings:

• No inline findings.

Generated at 2025-11-06T20:03:37.247Z.