refactor: dogfood setup-pnpm, pr-status-comment, trigger-website-update

[baxyz]

Summary

• Stacked on feat: add setup-pnpm, pr-status-comment, trigger-website-update actions #12 (adds the 3 new composite actions) — CI on this PR will show red until feat: add setup-pnpm, pr-status-comment, trigger-website-update actions #12 merges to main, since these workflows reference helpers4/action/<name>@main, which only resolves once feat: add setup-pnpm, pr-status-comment, trigger-website-update actions #12 is merged. This is expected, not a bug.
• pr-validation.yml:
  • shellcheck job now uses ludeeus/action-shellcheck (350★, already does this) instead of a hand-rolled apt-get + shellcheck sequence
  • The ~90-line status-comment actions/github-script block is replaced by one call to helpers4/action/pr-status-comment@main
  • Every job's "Set status" step + outputs: status: ... block is deleted — needs.<job>.result already exposes success/failure/skipped/cancelled natively, no custom output plumbing was ever needed
  • Net: 160 lines removed from this file alone
• release.yml: the Trigganator token + repository-dispatch steps collapse into one helpers4/action/trigger-website-update@main call (same continue-on-error: true, same non-blocking behavior as before)
• setup-pnpm isn't dogfooded here — this repo has no Node/pnpm build step of its own (bash-only actions), so there's nothing in this repo's CI for it to replace. It'll get its first real exercise when rolled out to typescript/website in a later pass (tracked in TODO.md).

Test plan

• CI on this PR will fail until feat: add setup-pnpm, pr-status-comment, trigger-website-update actions #12 merges (see above) — re-run once that lands
• After feat: add setup-pnpm, pr-status-comment, trigger-website-update actions #12 merges and this is re-run green: confirm the PR status comment renders correctly and the release workflow's dry-run-equivalent (dispatch step) still fires non-blocking on failure

🤖 Generated with Claude Code

[github-actions]

✅ PR Validation Passed

All checks passed!

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📋 Pipeline Status

	Job	Status
✅	🧾 Conventional Commits	passing
✅	🐚 ShellCheck	passing
✅	🧪 Action Tests	passing
✅	📄 Manifest Validation	passing
✅	📦 setup-pnpm Tests	passing
✅	💬 pr-status-comment Tests	passing

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_{🤖 Generated by @helpers4 CI • 2026-07-28}