skills/pr-review: clarify AGENTS.md rule updates and remove assumptions of /learn on Claude Code / Sonnet review lanes

[JoshuaVSherman]

Summary

Implements web-jam-tools#867: clarifies AGENTS.md and docs/cross-ai-rules.md scope exemptions in skills/pr-review/SKILL.md and removes assumptions of the /learn slash command on Claude Code (Sonnet) review lanes.

• skills/pr-review/SKILL.md: Updates Step 4 (Issue Acceptance Criteria & Scope) to clarify that AGENTS.md and docs/cross-ai-rules.md updates (whether learned interactively during task work or sourced from /learn on Antigravity sessions) are cross-cutting instruction content and never scope violations. Explicitly documents that /learn is an Antigravity-specific slash command that does not exist in Claude Code (Sonnet), and instructs reviewers never to expect or flag a missing /learn invocation.
• scripts/handle-agy-tasks.sh: Updates task prompt instructions under web-jam-tools#239 to scope /learn invocations to Antigravity sessions while noting non-Antigravity surfaces (e.g. Claude Code) continue without /learn.
• test/skills_validation.test.ts: Adds unit test verifying pr-review/SKILL.md documents AGENTS.md scope exemptions and Antigravity-specific /learn command.
• Version Bump: Bumps deno.json version to 1.32.33.

Closes #867

How to test locally

1. Skill Validation Unit Test:
   • Run deno test --allow-read test/skills_validation.test.ts and verify all 43 tests pass (including the new test verifying pr-review/SKILL.md rule exemptions and /learn Antigravity scoping).
2. Installers & Surface Consistency:
   • Run deno test --allow-all test/install_skills.test.ts and verify all 21 installer tests pass.
3. CI Gates & Static Analysis:
   • Run deno task fmt:check, deno task lint, and deno task sast to verify clean formatting, linting, and security audits.
   • Run deno task test to verify the full test suite (1939 tests) executes 100% green.

Test evidence

- deno task fmt:check: 201 files checked cleanly.
- deno task lint: 165 files checked cleanly.
- deno task sast: 0 security findings.
- deno test --allow-read test/skills_validation.test.ts: 43 passed, 0 failed.
- deno task test: 1939 passed, 0 failed (1m19s).

🤖 Work by Antigravity — Gemini Flash (High)