Run slow source-lint guards in parallel

.github/workflows/ci-guards.yml

@@ -563,7 +563,13 @@ jobs:
 
   workflow-guard-source-lints:
     if: ${{ inputs.linux_guard_source == 'true' }}
-    # Slow guards run beside workflow-guard-tests so they do not extend it.
+    name: workflow-guard-source-lints / ${{ matrix.group }}
+    strategy:
+      fail-fast: false
+      matrix:
+        group: [sidebar-layout, dispatch-ownership]
+    # These source-policy scans are independent and each dominates wall time;
+    # run them concurrently and aggregate through the reusable-workflow job.
     runs-on: ${{ vars.LINUX_RUNNER || 'blacksmith-4vcpu-ubuntu-2404' }}
     timeout-minutes: 15
     permissions:
@@ -582,13 +588,20 @@ jobs:
       - name: Install workflow guard Python dependencies
         run: python3 -m pip install --disable-pip-version-check --no-input PyYAML==6.0.3 bashlex==0.18
 
+      - name: Validate source-lint guard structure
+        if: ${{ matrix.group == 'sidebar-layout' }}
+        run: python3 tests/test_ci_source_lint_guard_structure.py
+
       - name: Validate sidebar lazy-layout guard
+        if: ${{ matrix.group == 'sidebar-layout' }}
         run: python3 tests/test_ci_sidebar_lazy_layout_guard.py
 
       - name: Initialize Bonsplit for deferred-work ownership guard
+        if: ${{ matrix.group == 'dispatch-ownership' }}
         run: git submodule update --init --depth 1 vendor/bonsplit
 
       - name: Validate stored DispatchWorkItem ownership
+        if: ${{ matrix.group == 'dispatch-ownership' }}
         run: |
           python3 tests/test_lint_stored_dispatch_work_items.py
           python3 scripts/lint-stored-dispatch-work-items.py

tests/test_ci_source_lint_guard_structure.py

@@ -0,0 +1,51 @@
+#!/usr/bin/env python3
+"""Structural contract for the reusable source-lint guard lane."""
+
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[1]
+GUARD_WORKFLOW = ROOT / ".github" / "workflows" / "ci-guards.yml"
+
+
+def workflow_job_block(job_name: str) -> str:
+    lines = GUARD_WORKFLOW.read_text(encoding="utf-8").splitlines()
+    marker = f"  {job_name}:"
+    for index, line in enumerate(lines):
+        if line != marker:
+            continue
+        body = [line]
+        for following in lines[index + 1 :]:
+            if (
+                following.startswith("  ")
+                and not following.startswith("    ")
+                and following.strip()
+            ):
+                break
+            body.append(following)
+        return "\n".join(body)
+    raise AssertionError(f"{job_name} job not found")
+
+
+def test_source_lint_matrix_runs_independent_slow_scans_in_parallel() -> None:
+    block = workflow_job_block("workflow-guard-source-lints")
+
+    assert "name: workflow-guard-source-lints / ${{ matrix.group }}" in block
+    assert "group: [sidebar-layout, dispatch-ownership]" in block
+    assert (
+        "- name: Validate sidebar lazy-layout guard\n"
+        "        if: ${{ matrix.group == 'sidebar-layout' }}"
+    ) in block
+    assert (
+        "- name: Initialize Bonsplit for deferred-work ownership guard\n"
+        "        if: ${{ matrix.group == 'dispatch-ownership' }}"
+    ) in block
+    assert (
+        "- name: Validate stored DispatchWorkItem ownership\n"
+        "        if: ${{ matrix.group == 'dispatch-ownership' }}"
+    ) in block
+
+
+if __name__ == "__main__":
+    test_source_lint_matrix_runs_independent_slow_scans_in_parallel()
+    print("PASS: source-lint guard workflow structure")