Add yamllint to workflow-validation CI (Phase 4 #G)

.github/workflows/ci.yml

@@ -214,7 +214,7 @@ jobs:
       - uses: actions/setup-python@v5
         with:
           python-version: "3.12"
-      - run: python -m pip install --upgrade pip pyyaml
+      - run: python -m pip install --upgrade pip pyyaml yamllint
       - name: Validate workflow YAML syntax
         run: |
           python - <<'PY'
@@ -226,6 +226,8 @@ jobs:
               yaml.safe_load(handle)
           print("Workflow YAML validation passed.")
           PY
+      - name: yamllint workflows (real YAML errors — see .yamllint)
+        run: yamllint -c .yamllint .github/workflows/
 
   # Single always-running aggregation gate. Make THIS the only required
   # branch-protection check (plus operability-gate). It understands a valid

.yamllint

@@ -0,0 +1,9 @@
+# yamllint config for OpenBlade — catches real YAML errors (syntax, duplicate keys,
+# bad indentation) without flagging harmless style. Applied to CI workflows.
+extends: default
+rules:
+  line-length: disable        # workflow run: lines are legitimately long
+  document-start: disable     # GitHub workflows do not use '---'
+  comments-indentation: disable
+  truthy:
+    check-keys: false         # allow the GitHub Actions 'on:' key