* ci: rebuild MLX macOS test payloads the release can't supply
The MLX unit test dependency payload can go stale when a PR changes the
xgrammar wrapper (release dylib lacks the new symbols) or bumps MLX pins (no
matching release, so MLX tests silently skipped). Compare the matched tag's
build rules and wrapper sources against the checkout, rebuilding only
libollama_xgrammar.dylib on drift; with no matching release, build one Metal
variant at the platform default.
* address comments
* ci: wire up MLX unit tests for PR runs
Download the latest Darwin release payload matching the current MLX and MLX-C revisions so macOS PR tests can exercise MLX without rebuilding it. If no matching release exists after a pin bump, leave MLX tests skipped until the next release.
Add whole-tree race coverage and smoke-run committed benchmarks. Verify generated UI types, and stabilize tests exposed by the broader CI coverage.
* review comments
* mlx: run tests on one pinned worker
Keep MLX tests and benchmarks on a shared pinned thread while preserving Fatal, Skip, and Cleanup semantics. Also clean stale CI payloads and ensure updater workers shut down cleanly.
* addres comments
