Add /review-pr skill and wire it into the Claude Code Review workflow

.claude/commands/review-pr.md

@@ -0,0 +1,135 @@
+---
+description: Produce a structured PR review for cowprotocol/services. Invoked locally as `/review-pr` (diff mode, against current branch vs main) or `/review-pr <N|url>` (PR mode). Same command also runs in CI via `.github/workflows/claude-code-review.yml`, where it posts a single review comment instead of printing to terminal. Read-only in local modes; the user posts any comments manually.
+---
+
+Review PR: $ARGUMENTS
+
+Follow the instructions in `./docs/COW_PR_REVIEW_SKILL.md` to produce the review report.
+
+## Prologue (execute in order; abort on any failure)
+
+### 1. Detect mode
+
+The skill runs in one of three modes. Detection:
+
+- If the environment variable `$GITHUB_ACTIONS == "true"` → `mode = "pr-ci"`.
+  - `$ARGUMENTS` MUST be a PR number, URL, or `owner/repo#N` form (the workflow passes it).
+- Else if `$ARGUMENTS` is non-empty → `mode = "pr-local"`. Parse the argument (see [step 2](#2-parse-arguments-pr-modes-only)).
+- Else (`$ARGUMENTS` empty, not in CI) → `mode = "diff"`. No `gh` calls needed; source is `git diff $(git merge-base HEAD main)..HEAD`.
+
+### 2. Parse $ARGUMENTS (PR modes only)
+
+*(Skip in `diff` mode.)*
+
+Accept any of:
+
+- A PR number: `4267`
+- A full URL: `https://github.com/cowprotocol/services/pull/4267`
+- An `owner/repo#N` form: `cowprotocol/services#4267`
+
+Default `owner/repo` to `cowprotocol/services` when only a number is given.
+
+Extract: `<PR_NUMBER>`, `<owner>`, `<repo>`.
+
+If unparseable, print and abort:
+
+```
+Usage: /review-pr                       # diff mode (current branch vs main)
+       /review-pr <PR_NUMBER>           # PR mode
+       /review-pr https://github.com/owner/repo/pull/<N>
+       /review-pr owner/repo#<N>
+```
+
+### 3. Diff-mode preflight
+
+*(Only in `mode == "diff"`.)*
+
+Run:
+
+```bash
+git fetch origin main --quiet
+BASE=$(git merge-base HEAD origin/main)
+git diff --stat "$BASE..HEAD"
+```
+
+If `git diff "$BASE..HEAD"` is empty, print `No diff vs main — nothing to review.` and exit clean (not an error).
+
+There is **no** clean-tree check, **no** rebase, and **no** `git pull` of main. Diff scope comes from the fetched `origin/main` merge-base.
+
+### 4. PR-mode preflight
+
+*(Only in `mode == "pr-local"` or `mode == "pr-ci"`.)*
+
+#### 4a. Working tree (pr-local only)
+
+Run `git status --porcelain`. If non-empty, print it plus:
+
+```
+Working tree is dirty. Stash or commit your changes, then re-run.
+
+  git stash        # temporary
+  git stash pop    # to restore later
+```
+
+Then **abort**. Never auto-stash.
+
+#### 4b. Save the current branch (pr-local only)
+
+Save the current branch name to `<prior_branch>` so the report's NEXT STEPS footer can suggest `git switch <prior_branch>` when the review is done.
+
+#### 4c. Fetch base ref
+
+Run `git fetch origin --quiet`. This makes the diff comparable to base without rebasing or modifying the user's branch.
+
+#### 4d. Checkout the PR
+
+Run `gh pr checkout <PR_NUMBER> -R <owner>/<repo>`. Failure handling:
+
+- **`gh` not installed** → print `Install gh: https://cli.github.com/` and abort.
+- **Auth error** → print `gh auth status` output plus `Run: gh auth login` and abort.
+- **PR doesn't exist / wrong repo** → surface `gh`'s error verbatim and abort.
+- **Fork without checkout permission** → switch to **degraded static-diff mode**:
+  - Set `mode_qualifier = "degraded static-diff"`.
+  - In the reference doc's §2, replace `gh pr diff <N>` with `gh pr diff <N> --patch -R <owner>/<repo>`.
+  - Flag the qualifier in the report header's `Mode:` line.
+- **Any other error** → surface verbatim and abort.
+
+In `pr-ci`, the workflow has already checked out the PR branch — skip 4d and just verify `HEAD` matches the expected ref.
+
+### 5. Optional-tooling probe
+
+Detect which optional accelerators are available in the current session: Serena MCP (`mcp__plugin_serena_serena__*`), `actionbook/rust-skills` (`rust-call-graph`, `rust-symbol-analyzer`, `rust-trait-explorer`, `rust-code-navigator`), `ra-qm-skills`, the `m04`/`m06`/`m07`/`m15` modules, `unsafe-checker`.
+
+Build a `loaded_context` list of whichever ones resolved. Pass it through to the reference doc; it prints verbatim in the report header's `Loaded context:` line.
+
+Do not abort if a skill is missing. Do not print install banners.
+
+### 6. Noise filter (before handoff)
+
+Classify each changed file:
+
+**Review surface (read fully):**
+
+- Anything under `crates/*/src/**/*.rs` (excluding `contracts/generated/**`).
+- `crates/e2e/tests/**/*.rs`.
+- `contracts/solidity/**/*.sol` (authored Solidity).
+- Config files: `**/openapi.yml`, `database/sql/**`, `configs/**`, semantically interesting `*.toml`.
+
+**Noise (skip or skim):**
+
+- `Cargo.lock` (any). CI validates the resolution; reviewing the lockfile diff is high-cost, low-signal.
+- `contracts/generated/**` and `contracts/artifacts/**` — machine-generated bindings and ABI JSON.
+- Auto-generated `Cargo.toml` entries from contract-binding crates.
+- Binary fixtures, ABI blobs, snapshot files.
+
+Report the filter in the report's `Scope:` line as `+X −Y across Z files (~N LOC human-written; rest generated/lockfile, filtered)`.
+
+### 7. Handoff
+
+Read `docs/COW_PR_REVIEW_SKILL.md` and follow it from §2 (Metadata Fetch) onward, passing through:
+
+- `mode` (`diff` / `pr-local` / `pr-ci`) and `mode_qualifier` if set.
+- `<PR_NUMBER>`, `<owner>`, `<repo>` (PR modes only).
+- `prior_branch` (`pr-local` only).
+- `loaded_context` (optional skills detected in step 5).
+- The noise-filter classification from step 6 — the reference doc uses it to decide what to read.

.github/workflows/claude-code-review.yml

@@ -18,14 +18,17 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
         with:
-          fetch-depth: 1
+          # Full history is needed so the skill's `git blame`-based
+          # historic-context step can resolve any line in the diff.
+          fetch-depth: 0
 
       - name: Run Claude Code Review
         id: claude-review
         uses: anthropics/claude-code-action@e0f2d99545298b87c2f984ab534af3a6534142ae # v1
         with:
           anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
-          plugin_marketplaces: 'https://github.com/anthropics/claude-code.git'
-          plugins: 'code-review@claude-code-plugins'
-          prompt: '/code-review:code-review ${{ github.repository }}/pull/${{ github.event.pull_request.number }} --comment'
-
+          # Invoke the in-repo slash command. The skill detects
+          # $GITHUB_ACTIONS=true and switches to `pr-ci` mode, posting
+          # a single consolidated review comment instead of streaming
+          # to a terminal. Skill source of truth: docs/COW_PR_REVIEW_SKILL.md
+          prompt: '/review-pr ${{ github.repository }}#${{ github.event.pull_request.number }}'