Add lint-checks composite action (prettier/eslint/commitlint, opt-in)

lint-checks/action.yaml

@@ -1,10 +1,10 @@
 name: lint-checks
 description: >
-  Node formatting, linting, and conventional-commit checks: prettier
-  (`format:check`) and eslint (`lint`) npm scripts, each `--if-present`,
-  plus commitlint if the repo has a commitlint config. Run after
-  actions/checkout and npm ci (e.g. after node-checks), in a job with node
-  available.
+  Style and hygiene checks: prettier (via the repo's format:check script),
+  eslint (via the repo's lint script), and conventional-commit linting when
+  a commitlint config exists. Each check is --if-present/config-gated, so
+  repos opt in by defining the script or config. Run after node-checks in
+  the same job (needs node_modules from npm ci).
 runs:
   using: composite
   steps:
@@ -13,18 +13,9 @@ runs:
     - run: npm run lint --if-present
       shell: bash
     - shell: bash
-      env:
-        GITHUB_EVENT_NAME: ${{ github.event_name }}
-        GITHUB_BASE_REF: ${{ github.base_ref }}
       run: |
-        set -euo pipefail
         if ls commitlint.config.* .commitlintrc* >/dev/null 2>&1; then
-          if [ "$GITHUB_EVENT_NAME" = "pull_request" ]; then
-            git fetch origin "$GITHUB_BASE_REF" --depth=1
-            npx --yes commitlint --from "origin/$GITHUB_BASE_REF" --to HEAD
+          npx --no-install commitlint --last --verbose
         else
-            npx --yes commitlint --from HEAD~1 --to HEAD
-          fi
-        else
-          echo "no commitlint config found, skipping conventional-commit check"
+          echo "no commitlint config, skipping conventional-commit check"
         fi