Add architecture marker coverage guard test

Co-authored-by: Shri Sukhani <shrisukhani@users.noreply.github.com>

Author: cursoragent

CONTRIBUTING.md

@@ -84,7 +84,8 @@ This runs lint, format checks, compile checks, tests, and package build.
   - `tests/test_display_helper_usage.py` (display/key-format helper usage),
   - `tests/test_ci_workflow_quality_gates.py` (CI guard-stage + make-target enforcement),
   - `tests/test_makefile_quality_targets.py` (Makefile quality-gate target enforcement),
-  - `tests/test_pyproject_architecture_marker.py` (pytest marker registration enforcement).
+  - `tests/test_pyproject_architecture_marker.py` (pytest marker registration enforcement),
+  - `tests/test_architecture_marker_usage.py` (architecture marker coverage across guard modules).
 
 ## Code quality conventions
 

tests/test_architecture_marker_usage.py

@@ -0,0 +1,25 @@
+from pathlib import Path
+
+import pytest
+
+pytestmark = pytest.mark.architecture
+
+
+ARCHITECTURE_GUARD_MODULES = (
+    "tests/test_guardrail_ast_utils.py",
+    "tests/test_manager_model_dump_usage.py",
+    "tests/test_mapping_reader_usage.py",
+    "tests/test_mapping_keys_access_usage.py",
+    "tests/test_tool_mapping_reader_usage.py",
+    "tests/test_display_helper_usage.py",
+    "tests/test_ci_workflow_quality_gates.py",
+    "tests/test_makefile_quality_targets.py",
+    "tests/test_pyproject_architecture_marker.py",
+    "tests/test_architecture_marker_usage.py",
+)
+
+
+def test_architecture_guard_modules_are_marked():
+    for module_path in ARCHITECTURE_GUARD_MODULES:
+        module_text = Path(module_path).read_text(encoding="utf-8")
+        assert "pytestmark = pytest.mark.architecture" in module_text