ci: build, lint, and test on macOS

[Karib0u]

Summary

Adds macOS to CI so the newly supported macOS target is built, linted, and tested on every push — closing the gap that let a macOS-only test regression slip through review on #42.

• clippy-macos and test-macos jobs on macos-latest, mirroring the self-contained Windows jobs (no eBPF artifact needed).
• Wired both into the release gate alongside the existing Linux/Windows jobs.
• Updated the stale "both platforms" Clippy comment to "all platforms".

Context

While reviewing #42 (first of the four-PR macOS series in #41), a tests/reload.rs failure was found that only reproduces on macOS — CI never would have caught it because there was no macOS runner. This adds that runner.

Follow-up

After this merges, add Clippy (macOS) and Tests (macOS) to the branch-protection required status checks so they block, not just report.

🤖 Generated with Claude Code

[Karib0u]

Closing — the macOS CI job can't pass against main because main isn't macOS-warning-clean until #42 lands (dead code in logging.rs / main.rs that #42 makes live). The two are coupled, so the CI job is being folded into #42 instead. The commit (d6479ea) remains on the feat/macos-platform branch as a cherry-pick reference.