Reap child when capture_output errors in CommandRunner::run

[Finesssee]

Closes #400.

The early ? on capture_output in CommandRunner::run propagated errors immediately, dropping the Child without kill()/wait() — a zombie on Unix until parent exit. Now routes the error through finish_child (the same kill+wait+recover teardown used by every other path since #398/#399) before propagating.

Verification: cargo build, cargo clippy --all-targets -- -D warnings, and cargo test (1365 passed) all green on a clean origin/main + this patch. Note: the current repo checkout carries unrelated concurrent WIP in rust/src/logging.rs that fails to compile on its own; it is not part of this PR.

Summary by CodeRabbit

• Bug Fixes
  • Improved handling of output-capture failures by safely cleaning up the running process before reporting an error.
  • Preserved existing behavior for successful command execution and output capture.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 40de7547-24fd-4a83-b392-4fcf9316f9f0

📥 Commits

Reviewing files that changed from the base of the PR and between a84ffb5 and c1f6e19.

📒 Files selected for processing (1)

• rust/src/host/command_runner.rs

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📝 Walkthrough

Walkthrough

CommandRunner::run now cleans up the child process when output capture fails. Successful output capture and result construction remain unchanged.

Changes

Command runner cleanup

Layer / File(s)	Summary
Capture failure cleanup rust/src/host/command_runner.rs	Output-capture errors now trigger finish_child before CommandRunner::run returns the error.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to c1f6e

The change ensures a child process is cleaned up before a capture error is returned, preventing lingering processes without introducing an identified merge-blocking risk. It is merge-ready after normal checks and review.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the main change: reaping the child process when output capture fails in CommandRunner::run.
Linked Issues check	✅ Passed	The change satisfies issue #400 by routing capture_output failures through child cleanup before returning the original error, preventing unreaped Unix zombie processes.
Out of Scope Changes check	✅ Passed	The seven added lines and one removed line directly implement the linked issue objective. No unrelated changes are reported.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 1 files.

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Create stacked PR
• Commit on current branch

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/capture-output-reap-child

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