test: reorganize test structure and add missing unit tests

Reorganize flat tests/ directory to mirror source code structure
(tools/, gateway/, hermes_cli/, integration/). Add 11 new test files
covering previously untested modules: registry, patch_parser,
fuzzy_match, todo_tool, approval, file_tools, gateway session/config/
delivery, and hermes_cli config/models. Total: 147 unit tests passing,
9 integration tests gated behind pytest marker.

tests/conftest.py

@@ -0,0 +1,38 @@
+"""Shared fixtures for the hermes-agent test suite."""
+
+import os
+import sys
+import tempfile
+from pathlib import Path
+from unittest.mock import patch
+
+import pytest
+
+# Ensure project root is importable
+PROJECT_ROOT = Path(__file__).parent.parent
+if str(PROJECT_ROOT) not in sys.path:
+    sys.path.insert(0, str(PROJECT_ROOT))
+
+
+@pytest.fixture()
+def tmp_dir(tmp_path):
+    """Provide a temporary directory that is cleaned up automatically."""
+    return tmp_path
+
+
+@pytest.fixture()
+def mock_config():
+    """Return a minimal hermes config dict suitable for unit tests."""
+    return {
+        "model": "test/mock-model",
+        "toolsets": ["terminal", "file"],
+        "max_turns": 10,
+        "terminal": {
+            "backend": "local",
+            "cwd": "/tmp",
+            "timeout": 30,
+        },
+        "compression": {"enabled": False},
+        "memory": {"memory_enabled": False, "user_profile_enabled": False},
+        "command_allowlist": [],
+    }