[HFH-4795] Agentic acceptance criteria

[garettarrowood]

Summary

Adds a reusable agentic-acceptance-criteria action that generates a non-technical manual QA plan from a pull request’s merge-base diff and posts it as an updatable PR comment.

What changed

• Added a composite action that:
  • Reuses the existing agentic-review GitHub App credentials and Cursor provider pool.
  • Checks out the PR head and computes the merge-base diff.
  • Runs Cursor with read-only repository permissions.
  • Uploads the raw generated JSON for debugging.
  • Upserts one authoritative acceptance-criteria comment instead of creating duplicates.
  • Preserves the last successful QA plan when a later run fails.
• Added a dedicated prompt that produces application-focused test coverage without relying on the PR description.
• Added structured parsing and deterministic Markdown formatting for:
  • Permissions and roles.
  • Functional test scenarios.
  • Regression testing.
• Added explicit fallback output when no manual application QA is identified.
• Documented the future nitro-web workflow using:
  • The agentic-acceptance-criteria label.
  • The /agentic-acceptance-criteria comment command.
  • No automatic PR-open, ready-for-review, or commit-push triggers.
• Documented the two-repository rollout and validation plan.

Example output

## ✅ Test Plan: PR #123 — Example change

---

### Permissions / Roles

- **Required Permissions:** Yes
- **Roles to Test:**
  - User with access to the affected feature

---

### Functional / Features to Test

#### Affected Feature

- **AF-1 — Default behavior**
  - Open the affected feature.
  - Verify the expected information appears.
  - Verify the updated behavior works as expected.

---

### Regression Testing

- Verify the neighboring workflow remains unchanged.
- Verify users cannot access data outside their permissions.

Validation

• 18 new examples passing across the parser, formatter, and command-line renderer.
• Ruby and shell syntax checks passing.
• Composite-action YAML validation passing.
• RuboCop lint checks passing.

Next steps

1. Merge this PR into github-actions-workflows.
2. Copy the resulting immutable commit SHA from main.
3. Create the agentic-acceptance-criteria label in nitro-web ✅
4. Open a separate nitro-web PR adding the documented acceptance-criteria workflow, pinned to that SHA.
5. After the workflow reaches nitro-web’s default branch, validate both trigger paths on an open PR:
   • Apply the agentic-acceptance-criteria label.
   • Comment /agentic-acceptance-criteria.
6. Confirm both paths update the same QA comment and do not trigger the existing code-review workflow.

[powerhome-portal]

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