[codex] fix(vscode): force-kill unresponsive reviews

[cosin2077]

Background

The VS Code extension sends SIGTERM when a user cancels an active review and is intended to escalate to SIGKILL after three seconds if the CLI process does not exit.

Root cause

ChildProcess.killed only indicates that a signal was successfully sent. It does not indicate that the child process has exited. A process that ignores SIGTERM therefore has killed === true while exitCode and signalCode remain null, preventing the existing timeout from ever sending SIGKILL.

Fix

• Check exitCode and signalCode to determine whether the child is still running before escalating to SIGKILL.
• Clear the escalation timer when the child emits close to avoid signaling a process that already exited.
• Add regression tests for both an unresponsive child and a child that exits normally after SIGTERM.

Verification

• yarn install --frozen-lockfile (Node.js 24.18.0)
• yarn lint - 0 errors (1 pre-existing warning in IdleView.tsx)
• yarn test --runInBand - 11 suites, 94/94 tests passed
• yarn build - production webpack build passed

Related

• feat(vscode): add VSCode extension for AI code review #95 introduced the VS Code extension and its cancellation flow.

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[github-actions]

✅ OpenCodeReview: No comments generated. Looks good to me.