Add display key-format import boundary guard

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

Author: cursoragent

CONTRIBUTING.md

@@ -121,6 +121,7 @@ This runs lint, format checks, compile checks, tests, and package build.
   - `tests/test_default_terminal_status_helper_usage.py` (default terminal-status helper usage enforcement for non-agent managers),
   - `tests/test_display_blank_key_literal_boundary.py` (blank-key display literal centralization in `hyperbrowser/display_utils.py`),
   - `tests/test_display_helper_usage.py` (display/key-format helper usage),
+  - `tests/test_display_key_format_import_boundary.py` (display key-format helper import boundary enforcement),
   - `tests/test_docs_python3_commands.py` (`README`/`CONTRIBUTING`/examples python3 command consistency enforcement),
   - `tests/test_example_run_instructions.py` (example run-instruction consistency enforcement),
   - `tests/test_example_sync_async_parity.py` (sync/async example parity enforcement),

tests/test_architecture_marker_usage.py

@@ -51,6 +51,7 @@
     "tests/test_tool_mapping_reader_usage.py",
     "tests/test_display_blank_key_literal_boundary.py",
     "tests/test_display_helper_usage.py",
+    "tests/test_display_key_format_import_boundary.py",
     "tests/test_file_open_default_prefix_literal_boundary.py",
     "tests/test_file_message_default_constant_import_boundary.py",
     "tests/test_file_message_default_constant_usage.py",

tests/test_display_key_format_import_boundary.py

@@ -0,0 +1,42 @@
+import ast
+from pathlib import Path
+
+import pytest
+
+pytestmark = pytest.mark.architecture
+
+
+EXPECTED_KEY_FORMAT_HELPER_IMPORTERS = (
+    "hyperbrowser/client/managers/extension_utils.py",
+    "hyperbrowser/client/managers/response_utils.py",
+    "hyperbrowser/client/managers/session_utils.py",
+    "hyperbrowser/tools/__init__.py",
+    "hyperbrowser/transport/base.py",
+    "tests/test_display_utils.py",
+)
+
+
+def _imports_format_string_key_for_error(module_text: str) -> bool:
+    module_ast = ast.parse(module_text)
+    for node in module_ast.body:
+        if not isinstance(node, ast.ImportFrom):
+            continue
+        if any(alias.name == "format_string_key_for_error" for alias in node.names):
+            return True
+    return False
+
+
+def test_format_string_key_for_error_imports_are_centralized():
+    discovered_modules: list[str] = []
+
+    for module_path in sorted(Path("hyperbrowser").rglob("*.py")):
+        module_text = module_path.read_text(encoding="utf-8")
+        if _imports_format_string_key_for_error(module_text):
+            discovered_modules.append(module_path.as_posix())
+
+    for module_path in sorted(Path("tests").glob("test_*.py")):
+        module_text = module_path.read_text(encoding="utf-8")
+        if _imports_format_string_key_for_error(module_text):
+            discovered_modules.append(module_path.as_posix())
+
+    assert discovered_modules == list(EXPECTED_KEY_FORMAT_HELPER_IMPORTERS)