fix: restore green main - clippy needless borrow + unix pid-0 liveness (#1213 follow-up)

[zackees]

Closes #1213

Summary

PR #1227 was admin-merged with the Check jobs red, breaking main two ways. This PR fixes both:

1. Clippy hard error (needless_borrows_for_generic_args, daemon_cmd.rs:26): pass format!(...) by value instead of &format!(...) — output::result takes impl Display, and -D warnings turns the lint into an error. This is what turned Check Ubuntu/Windows red at the merge commit (green on the prior push, fix(ldf): honor lib_deps on Teensy/STM32 and warn on inert lib_ldf_mode (#1214) #1226).
2. Unix PID-liveness bug: pid_is_alive used kill(pid, 0) == 0, but kill(0, 0) probes the caller's own process group and succeeds — so PID 0 read as "alive" on macOS/Linux. That failed fix(packages,daemon): reclaim dead-owner install locks; stop leaving stale endpoint records (#1213) #1227's two install-lock staleness tests on Check macOS (Ubuntu masked behind the clippy error; Windows unaffected, which is why it slipped through local dev). It is also a real production hole: a corrupt owner.txt recording pid=0 would never be reclaimed — the exact Orphaned mkdir install-locks deadlock after daemon crash; stale daemon endpoint survives 'daemon stop'; esptool provisioning failure kills daemon #1213 deadlock class. Fixed with an explicit pid-0 guard + cross-platform regression test.

With this follow-up, all three parts of #1213 are fully landed (dead-owner install-lock reclaim + stale endpoint clearing shipped in #1227).

Validation

• soldr cargo clippy -p fbuild-cli --all-targets -- -D warnings — clean (previously reproduced the exact CI error).
• soldr cargo test -p fbuild-core process_identity — 7 passed (incl. new pid_zero_is_never_alive).
• soldr cargo test -p fbuild-packages-fetch install_lock — 12 passed.
• Root causes confirmed against CI logs: run 30720560199 (Check Ubuntu, main — clippy error) and job 91426904142 (Check macOS, this PR — the two install_lock test failures).

🤖 Generated with Claude Code

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

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Review profile: CHILL

Plan: Pro Plus

Run ID: 1311a7ca-0328-42f4-b59e-e5a602a4bb7a

📥 Commits

Reviewing files that changed from the base of the PR and between 5a0bc88 and 15a0ee1.

📒 Files selected for processing (1)

• crates/fbuild-cli/src/cli/daemon_cmd.rs

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📝 Walkthrough

Walkthrough

The daemon command now passes the formatted stale-record message directly to output::result. The displayed output remains unchanged.

Changes

Daemon output formatting

Layer / File(s)	Summary
Stale-record reporting crates/fbuild-cli/src/cli/daemon_cmd.rs	run_daemon passes the format! result directly to output::result.

Estimated code review effort: 1 (Trivial) | ~2 minutes

🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (2 warnings)

Check name	Status	Explanation	Resolution
Linked Issues check	⚠️ Warning	The change fixes Clippy but does not demonstrate the lock, endpoint, or esptool recovery requirements listed in issue #1213.	Provide links and evidence for the separate implementations, or include the missing #1213 changes in this pull request.
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (3 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 needless-borrow fix that resolves the Clippy failure.
Out of Scope Changes check	✅ Passed	The one-line change is directly related to the stated CLI follow-up and restores Clippy checks.

✨ Finishing Touches 💡 1

📝 Generate docstrings 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/main-clippy-needless-borrow

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