#20772 Fix base red: IdleOwnerRestart retry loop flagged by check-concurrency

Summary

• feat-cmux-next fails check-concurrency.sh on IdleOwnerRestart.swift:43 ("loop that can spin"), from c6390e5a6486a (cx-1ubql). It blocks the cmux-next checks job on every feat PR.
• The repeat loop in attempt() runs again only when another attempt() arrived while the probe was awaiting (again = true), so it is event-driven, not a poll. This adds the reviewed // wakeup-allow: comment the check asks for. No code change.

Testing

• scripts/cmux-next/check-concurrency.sh: 1 violation on base, ok on this head.

Changelog

none

🤖 Generated with Claude Code

---

^{Need help on this PR? Tag @codesmith-bot with what you need.}

---

Summary by cubic

Unblocks check-concurrency on feat-cmux-next by marking the retry loop in IdleOwnerRestart as wakeup-allow, so the check no longer flags it as a potential spin.

The loop only runs again when another attempt() arrives during the probe, so it is event-driven, not a poll. No code behavior changes.