[joeblau]

Speed up haptic CI on the self-hosted Mac mini runners ([self-hosted, macOS, ARM64]) without moving any job off the minis.

Timing (Oct 17–20)

Verified against Documentation workflow history:

• Pull-request build jobs always ran actions/upload-pages-artifact@v5 after docs:build / docs:smoke. Successful PR uploads were 7–70s (median ~43s among completed successes; the earlier analysis’s p50 of 35s is in the same range).
• The deploy job was skipped on every PR in that window (skipped or cancelled). Live smoke therefore never ran on PRs either.
• Same-repo PRs still need the build, type/docs checks, and Playwright smoke; they do not need a Pages artifact.

package-manager-cache: false is unchanged on every setup-node step. The minis keep their local npm cache.

Changes

1. Skip the Pages artifact on PRs (.github/workflows/docs.yml). actions/upload-pages-artifact@v5 and the gtar preflight now run only when github.event_name != 'pull_request'. Push-to-main and workflow_dispatch still upload so deploy can consume the artifact.
2. Keep PR docs validation. PRs still npm ci, npm run build, docs:check, docs:build, install Playwright, and docs:smoke. Failure artifacts are unchanged.
3. Cancel in-progress jobs on PRs only. Tests and Documentation already had a per-ref concurrency group, but cancel-in-progress: true also aborted in-flight main deploys. Both workflows now use cancel-in-progress: ${{ github.event_name == 'pull_request' }}. Publish npm stays cancel-in-progress: false.
4. Keep every job on the Mac minis. No runs-on change. Fork-PR skip guards from ci(security): skip self-hosted runner jobs for fork PRs #34 are unchanged.
5. Document the skip (docs/ci-runners.md): Pages artifact is for deploy, not PR validation; PR concurrency cancels superseded runs without cancelling main deploys.

Do not merge until Tests and Documentation are green on the minis for this PR.