#4311 ci(release): build the Limrun runner on the macos-27 image

Summary

Follow-ups to #4305, which merged before these landed:

• Release image: release-ios-runner.yml now runs on blacksmith-6vcpu-macos-27, where Xcode 27 is the default, and the "Select Xcode 27" step is deleted. That step had grown into enumeration, version parsing and ranking through review rounds; the image's default makes it unnecessary. scripts/package-ios-simulator-runner.sh still refuses a runner that embeds XCTest.framework, so a runner from an older Xcode cannot publish.
• Test: the unread-exit lifecycle test stops its virtual-time polling once the request settles, so an early startup failure fails with the named assertion instead of the 5 s test timeout (review on #4305).

2 files, net −21 lines. Refs #4301.

Validation

Head dcbe305423: pnpm check:affected --run --head dcbe305423 passed, exactCommit=true.

The lifecycle test passes. With a 150 ms real fixture setup it still passes, and with a failing setup it fails fast with its assertion.

Open risk: no other workflow in this repo uses blacksmith-6vcpu-macos-27. Blacksmith documents the label with Xcode 27 as default, but PR CI never runs this workflow. The first proof is the next release-ios-runner run; check it before the stable release.

🤖 Generated with Claude Code

---

^{Open in [code]smith · Need help on this PR? Tag @codesmith-bot with what you need.}