Add display blank-key literal boundary guard

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

Author: cursoragent

CONTRIBUTING.md

@@ -119,6 +119,7 @@ This runs lint, format checks, compile checks, tests, and package build.
   - `tests/test_core_type_helper_usage.py` (core transport/config/header/file/polling/session/error/parsing manager+tool module enforcement of shared plain-type helper usage),
   - `tests/test_default_serialization_helper_usage.py` (default optional-query serialization helper usage enforcement),
   - `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_docs_python3_commands.py` (`README`/`CONTRIBUTING`/examples python3 command consistency enforcement),
   - `tests/test_example_run_instructions.py` (example run-instruction consistency enforcement),

tests/test_architecture_marker_usage.py

@@ -49,6 +49,7 @@
     "tests/test_model_request_internal_reuse.py",
     "tests/test_model_request_wrapper_internal_reuse.py",
     "tests/test_tool_mapping_reader_usage.py",
+    "tests/test_display_blank_key_literal_boundary.py",
     "tests/test_display_helper_usage.py",
     "tests/test_file_open_default_prefix_literal_boundary.py",
     "tests/test_file_message_default_constant_import_boundary.py",

tests/test_display_blank_key_literal_boundary.py

@@ -0,0 +1,25 @@
+from pathlib import Path
+
+import pytest
+
+pytestmark = pytest.mark.architecture
+
+
+HYPERBROWSER_ROOT = Path(__file__).resolve().parents[1] / "hyperbrowser"
+ALLOWED_LITERAL_MODULE = Path("display_utils.py")
+BLANK_KEY_LITERAL = "<blank key>"
+
+
+def test_blank_key_literal_is_centralized_in_display_utils():
+    violations: list[str] = []
+
+    for module_path in sorted(HYPERBROWSER_ROOT.rglob("*.py")):
+        relative_path = module_path.relative_to(HYPERBROWSER_ROOT)
+        if relative_path == ALLOWED_LITERAL_MODULE:
+            continue
+        module_text = module_path.read_text(encoding="utf-8")
+        if BLANK_KEY_LITERAL not in module_text:
+            continue
+        violations.append(relative_path.as_posix())
+
+    assert violations == []