Add file-message prefix literal boundary guard

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

Author: cursoragent

CONTRIBUTING.md

@@ -135,6 +135,7 @@ This runs lint, format checks, compile checks, tests, and package build.
   - `tests/test_extension_request_internal_reuse.py` (extension request-helper internal reuse of shared model request helpers),
   - `tests/test_extension_route_constants_usage.py` (extension manager route-constant usage enforcement),
   - `tests/test_extract_payload_helper_usage.py` (extract start-payload helper usage enforcement),
+  - `tests/test_file_message_prefix_literal_boundary.py` (extension/session file-message prefix literal centralization in shared metadata modules),
   - `tests/test_file_open_error_helper_import_boundary.py` (shared file-open error-message helper import boundary enforcement),
   - `tests/test_file_open_error_helper_usage.py` (shared file-open error-message helper usage enforcement),
   - `tests/test_file_path_display_helper_import_boundary.py` (shared file-path display helper import boundary enforcement),

tests/test_architecture_marker_usage.py

@@ -50,6 +50,7 @@
     "tests/test_model_request_wrapper_internal_reuse.py",
     "tests/test_tool_mapping_reader_usage.py",
     "tests/test_display_helper_usage.py",
+    "tests/test_file_message_prefix_literal_boundary.py",
     "tests/test_file_open_error_helper_import_boundary.py",
     "tests/test_file_open_error_helper_usage.py",
     "tests/test_file_path_display_helper_import_boundary.py",

tests/test_file_message_prefix_literal_boundary.py

@@ -0,0 +1,35 @@
+from pathlib import Path
+
+import pytest
+
+pytestmark = pytest.mark.architecture
+
+
+HYPERBROWSER_ROOT = Path(__file__).resolve().parents[1] / "hyperbrowser"
+ALLOWED_LITERAL_MODULES = {
+    Path("client/managers/extension_operation_metadata.py"),
+    Path("client/managers/session_operation_metadata.py"),
+}
+FORBIDDEN_PREFIX_LITERALS = (
+    "Extension file not found at path",
+    "Extension file path must point to a file",
+    "Failed to open extension file at path",
+    "Upload file not found at path",
+    "Upload file path must point to a file",
+    "Failed to open upload file at path",
+)
+
+
+def test_file_message_prefix_literals_are_centralized_in_metadata_modules():
+    violations: list[str] = []
+
+    for module_path in sorted(HYPERBROWSER_ROOT.rglob("*.py")):
+        relative_path = module_path.relative_to(HYPERBROWSER_ROOT)
+        if relative_path in ALLOWED_LITERAL_MODULES:
+            continue
+        module_text = module_path.read_text(encoding="utf-8")
+        for literal in FORBIDDEN_PREFIX_LITERALS:
+            if literal in module_text:
+                violations.append(f"{relative_path}:{literal}")
+
+    assert violations == []