release.yml now stages the macOS runtime alongside the Linux tarballs and
mirrors it to GitHub with no manual steps. The aarch64-apple-darwin.tgz is
pulled from the shared headless runtime-<hash> release (published by
scripts/runtime-push.sh arm64 on mutsu), staged as
carbonyl-<version>-aarch64-apple-darwin.tgz (+ .sha256), and carried by the
existing Gitea-upload and GitHub-mirror loops with no further changes.

Gated by a default-on include_macos workflow_dispatch toggle. When true
(the default, including tag-push), a missing macOS runtime asset fails the
release loudly with remediation guidance rather than silently shipping
Linux-only; set include_macos=false for an interim Linux-only release.

macOS is headless-only (no x11 variant). arm64-linux remains a separate
triple, pending a published runtime (fathyb#116) before joining the matrix (fathyb#108).

Refs fathyb#113, fathyb#67

…n release.yml

Refs fathyb#113, fathyb#67

- RELEASE-v0.2.0-alpha.8.md: notes for the delta since alpha.7 — real
  accessibility-tree output for --dump-text=accessibility (fathyb#90), the net::
  log-prefix fix (fathyb#97), and automated macOS release-asset staging (fathyb#113/fathyb#117).
  Chromium patch stack unchanged at 30.
- package.json: 0.2.0-alpha.7 -> 0.2.0-alpha.8 (Cargo.toml version left as-is
  per convention; it is a runtime-hash input).
- changelog.md: regenerated via git-cliff — adds the alpha.8 section and
  backfills the previously-missing alpha.7 section.
- docs/ci-runner-mutsu.md: note that release.yml now auto-stages/mirrors the
  macOS asset; only the build trigger remains manual.

Runtime hash for this release: 283ca65ffeeaa2dc. Cutting the v0.2.0-alpha.8 tag
requires runtimes built for that hash (titan headless+x11; mutsu macOS, or cut
with include_macos=false for a Linux-only release).