add pr-review skill

plugin/skills/github-pr-review/SKILL.md

@@ -0,0 +1,65 @@
+---
+name: github-pr-review
+description: >
+  This skill should be used when the user asks to "review this PR", "review before I merge",
+  "is this safe to merge", "check this pull request", "code review", pastes a GitHub PR URL,
+  or asks for a merge gate / pre-merge check. Also triggers on "review the diff", "audit this
+  change", "any bugs in this PR", and requests to post review comments on GitHub.
+metadata:
+  version: "0.1.0"
+---
+
+# PR Review + Merge Gate
+
+Produce a review that catches real defects and posts them as line comments on GitHub — not a summary of what the diff does.
+
+## Gather before judging
+
+1. `pull_request_read` for metadata: base branch, head SHA, author, mergeable state, requested reviewers.
+2. Pull the diff. For anything over ~15 files, clone the repo into the session workspace and diff locally instead of paging the API.
+3. Check CI first. A red build makes most of the review moot — report the failure and stop unless the user wants the review anyway.
+4. Read the PR body against the repo's template. A missing test plan is itself a finding.
+
+## Review dimensions
+
+Run every dimension. Do not stop at the first finding.
+
+**Correctness** — off-by-one, null/undefined paths, unhandled promise rejections, wrong operator precedence, timezone and float arithmetic, missing early returns, state mutated during iteration.
+
+**Security** — injection (SQL, command, prompt), missing authz on a new endpoint, secrets committed in plaintext, overly permissive CORS, unvalidated user input reaching a query or file path, dependency added with a known CVE, `dangerouslySetInnerHTML`.
+
+**Data layer (Supabase/Postgres)** — N+1 query patterns, missing index on a new filter column, RLS policy absent on a new table, migration without a rollback path, `select *` in a hot path, missing transaction around multi-write.
+
+**Solidity (pair with `solidity-foundry`)** — reentrancy, unchecked external call return, missing access modifier, integer truncation on casts, oracle staleness not validated, unbounded loop over storage, `tx.origin` used for auth, missing event on state change, upgrade-unsafe storage layout change.
+
+**Frontend (React/TS)** — missing dependency in a hook array, state derived in render without memo on an expensive path, `any` escaping a public type boundary, uncontrolled re-renders from an inline object prop, missing error boundary on a new route.
+
+**Tests** — new behavior with no test, test that asserts the mock instead of the behavior, deleted test with no replacement, flake risk from timing or ordering assumptions.
+
+## Severity, and what earns each level
+
+| Level | Bar | Merge |
+|---|---|---|
+| **Blocking** | Reproducible incorrect behavior, security hole, or data loss. State the concrete input → wrong output. | No |
+| **Should fix** | Real defect with narrow blast radius, or a missing test on new logic. | Author's call |
+| **Note** | Style, naming, minor simplification. | Yes |
+
+If a finding cannot be expressed as "input X produces wrong result Y", it is a Note at most. Do not inflate.
+
+## Posting to GitHub
+
+Use the pending-review flow so all comments land as one review, not fifteen notifications:
+
+1. `pull_request_review_write` with method `create` — opens a pending review.
+2. `add_comment_to_pending_review` per finding, anchored to file and line, each stating the defect and the fix.
+3. `pull_request_review_write` with method `submit_pending` — event `REQUEST_CHANGES` if anything is Blocking, otherwise `COMMENT`.
+
+Never `APPROVE` on the user's behalf unless they explicitly ask for an approval.
+
+## Verify before posting
+
+For each Blocking finding, try to refute it before it goes on the record. Re-read the surrounding code for a guard you may have missed, check whether a caller already validates the input, and confirm the line numbers match the current head SHA. Drop anything that survives on vibes alone. A confidently wrong blocking comment costs more credibility than a missed nit.
+
+## Output to the user
+
+Lead with the verdict — **Merge / Merge after fixes / Do not merge** — then findings, most severe first, each with file:line and the concrete failure. Close with the review URL. No recap of what the PR does; the author wrote it.