docs(skills): strengthen UI review rules

[Alan-TheGentleman]

Context

Follow-up from the review on #11376 / PROWLER-1770.

That review surfaced three reusable process gaps in the UI skills: feature-local helper placement, stale UI error branches after contract changes, and missing negative tests for mapper/type-guard predicates.

Description

This PR strengthens the AI-agent skill guidance so future UI changes catch those issues earlier.

• Clarifies that feature/domain ownership beats raw usage count for helper placement
• Adds a required UI error-state replacement checklist
• Adds TypeScript guidance requiring negative tests for type guards and mapper predicates

Steps to review

1. Review skills/prowler-ui/SKILL.md for the feature-local helper and error-state checklist additions.
2. Review skills/typescript/SKILL.md for type guard negative-test guidance.
3. Confirm no generated AGENTS metadata changes are needed because skill metadata was not changed.

Checklist

Community Checklist

• This follow-up comes from PR review feedback in fix(ui): improve invitation error messages #11376 / PROWLER-1770
• Is it assigned to me, if not, request it via the issue/feature in Jira or Prowler Community Slack

• Review if the code is being covered by tests. Not applicable; documentation-only skill guidance.
• Review if code is being documented following this specification https://github.com/google/styleguide/blob/gh-pages/pyguide.md#38-comments-and-docstrings. Not applicable.
• Review if backport is needed. Not needed.
• Review if is needed to change the Readme.md. Not needed.
• Ensure new entries are added to CHANGELOG.md, if applicable. Not applicable; skill documentation only.

SDK/CLI

• Are there new checks included in this PR? No
  • If so, do we need to update permissions for the provider? Not applicable.

UI

• All issue/task requirements work as expected on the UI. Not applicable; no UI runtime changes.
• If this PR adds or updates npm dependencies, include package-health evidence (maintenance, popularity, known vulnerabilities, license, release age) and explain why existing/native alternatives are insufficient. Not applicable; no dependency changes.
• Screenshots/Video of the functionality flow (if applicable) - Mobile (X < 640px). Not applicable.
• Screenshots/Video of the functionality flow (if applicable) - Table (640px > X < 1024px). Not applicable.
• Screenshots/Video of the functionality flow (if applicable) - Desktop (X > 1024px). Not applicable.
• Ensure new entries are added to CHANGELOG.md, if applicable. Not applicable; skill documentation only.

API

• All issue/task requirements work as expected on the API. Not applicable.
• Endpoint response output (if applicable). Not applicable.
• EXPLAIN ANALYZE output for new/modified queries or indexes (if applicable). Not applicable.
• Performance test results (if applicable). Not applicable.
• Any other relevant evidence of the implementation (if applicable). Not applicable.
• Verify if API specs need to be regenerated. Not applicable.
• Check if version updates are required (e.g., specs, uv, etc.). Not applicable.
• Ensure new entries are added to CHANGELOG.md, if applicable. Not applicable.

License

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[github-actions]

✅ Conflict Markers Resolved

All conflict markers have been successfully resolved in this pull request.