Fix: list_background_processes prints (Exit Code: null) for signal-killed processes

[laxanarana1513]

Summary

• Stop printing (Exit Code: null) from list_background_processes when a background process has no numeric exit code (signal kill / exitCode: null).
• Guard the clause with typeof p.exitCode === 'number' in shellBackgroundTools.ts.
• Add unit tests for null, undefined, 0, and signal-only listings in src/tools/shellBackgroundTools.test.ts.

Details

No design decisions were made for this change.

Related Issues

Fixes #29167

How to Validate

Run npx vitest run src/tools/shellBackgroundTools.test.ts.

Pre-Merge Checklist

• Updated relevant documentation and README (if needed)
• Added/updated tests (if needed)
• Noted breaking changes (if any)
• Validated on required platforms/methods:
  • MacOS
    • npm run
    • npx
    • Docker
    • Podman
    • Seatbelt
  • Windows
    • npm run
    • npx
    • Docker
  • Linux
    • npm run
    • npx
    • Docker

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses an issue where background process listings incorrectly displayed '(Exit Code: null)' for processes that were killed by signals or lacked a numeric exit code. By tightening the validation logic, the tool now correctly omits the exit code clause in these cases, improving the clarity of the process status output.

Highlights

• Bug Fix: Updated the exit code display logic in list_background_processes to prevent printing '(Exit Code: null)' for processes terminated by signals.
• Code Improvement: Refined the conditional check to ensure the exit code is only displayed when it is a valid number.
• Testing: Added comprehensive unit tests covering null, undefined, numeric, and signal-only exit scenarios to ensure correct output formatting.

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[github-actions]

📊 PR Size: size/M

• Lines changed: 113
• Additions: +112
• Deletions: -1
• Files changed: 2

[gemini-code-assist]

Code Review

This pull request updates the list_background_processes tool in packages/core to correctly handle cases where a background process's exit code is null or undefined. Specifically, it changes the check from p.exitCode !== undefined to typeof p.exitCode === 'number' to ensure that exit codes are only displayed when they are numeric. Additionally, several unit tests have been added to verify this behavior under various scenarios (null exit code, undefined exit code, exit code 0, and signaled exits). There are no review comments, so I have no feedback to provide.

[github-actions]

🛑 Action Required: Evaluation Approval

Steering changes have been detected in this PR. To prevent regressions, a maintainer must approve the evaluation run before this PR can be merged.

Maintainers:

1. Go to the Workflow Run Summary.
2. Click the yellow 'Review deployments' button.
3. Select the 'eval-gate' environment and click 'Approve'.

Once approved, the evaluation results will be posted here automatically.