v0.1.2

CI and build-gate changes only; no crate code changed since 0.1.1.

Changed

• CI dependency reuse and shorter queues. Linux default/io-uring/predict
  tests run independently; the Metal and PTY tests share a dependency graph
  with the conformance pass. External dependency caches accelerate ordinary
  test jobs while release CI keeps a clean full gate. Superseded ordinary
  main CI is cancelled; known documentation-only changes can skip Rust jobs
  under a tested required-check policy. Stress builds once per OS and retains
  all three thread counts and their iteration weights. Cargo timing artifacts
  make compilation costs inspectable; no benchmarked speedup is claimed yet.
• make gate includes MSRV, the complete macOS Metal lane, and all-feature
  documentation and dependency-policy checks to match the CI requirements.

Fixed

• The crate-metadata gate runs under macOS's bundled Bash 3.2, preserving
  empty-field validation without the unavailable mapfile builtin.
• The MSRV target invokes Rustup explicitly, so a standalone Cargo earlier
  on PATH cannot bypass the declared compiler selection.