fix(review-pr): remove auto-review, require explicit reviewer request only

[derekmisler]

Summary

Reviews now only run when docker-agent is explicitly requested as a reviewer (review_requested). Auto-review on opened/ready_for_review is removed everywhere.

Changes

.github/workflows/pr-review-trigger.yml (new canonical fork-PR trigger template):

• Only review_requested trigger type (removed opened, ready_for_review)
• Concurrency group to deduplicate simultaneous events for the same PR
• if: github.event.pull_request.head.repo.fork && github.event.sender.type != 'Bot' — only runs for fork PRs, skips Bot-account senders early

.github/workflows/review-pr.yml:

• Removed the auto-review pull_request branch (action != 'review_requested') from the review job if: condition
• Updated trigger-type classification comment to reflect explicit-only model

review-pr/README.md:

• Removed all auto-review language and Mode A/B trigger mode section
• Updated all workflow snippets to review_requested only
• Updated trigger table (removed "PR opened/ready" row), flow diagram, and defense-in-depth section

.agents/skills/add-pr-reviewer-to-repo/SKILL.md:

• Removed trigger mode selection section (Modes A/B)
• Updated all YAML templates to review_requested only
• Updated fork trigger template with concurrency group and if condition
• Updated audit checklist to check for review_requested only

[docker-agent]

Assessment: 🟢 APPROVE

The changes look correct. This PR cleanly removes auto-review triggers (opened, ready_for_review) and restricts triggering to explicit review_requested events only.

Reviewed areas:

• .github/workflows/pr-review-trigger.yml — new if: guard on save-context job correctly handles both pull_request and pull_request_review_comment events. The pull_request_review_comment webhook payload includes a nested pull_request object (per GitHub docs), so github.event.pull_request.head.repo.fork is valid and populated for both event types. ✅
• .github/workflows/review-pr.yml — removed auto-review branch from if: condition. Logic is consistent with the new explicit-only model. ✅
• review-pr/README.md — documentation updated to reflect review_requested-only model. Examples are accurate. ✅
• .agents/skills/add-pr-reviewer-to-repo/SKILL.md — simplified documentation template matches the actual workflow guard semantics. ✅

No bugs found in the changed code.