feat: harden seat intent and expand HIL coverage

tests/unit/test_config_loader.py

@@ -0,0 +1,46 @@
+from __future__ import annotations
+
+import os
+import tempfile
+import unittest
+from pathlib import Path
+from unittest.mock import patch
+
+from cognitive_agent.config_loader import load_local_env
+
+
+class LocalEnvironmentLoaderTests(unittest.TestCase):
+    def test_file_replaces_blank_inherited_value_but_preserves_non_blank_override(self) -> None:
+        with tempfile.TemporaryDirectory() as directory:
+            path = Path(directory) / ".env"
+            path.write_text(
+                "OPENAI_MODEL=gpt-5.6-sol\nOPENAI_BASE_URL=https://configured.example/v1\n",
+                encoding="utf-8",
+            )
+            with patch.dict(
+                os.environ,
+                {
+                    "OPENAI_MODEL": "",
+                    "OPENAI_BASE_URL": "https://explicit.example/v1",
+                },
+                clear=True,
+            ):
+                load_local_env(path)
+                self.assertEqual(os.environ["OPENAI_MODEL"], "gpt-5.6-sol")
+                self.assertEqual(
+                    os.environ["OPENAI_BASE_URL"], "https://explicit.example/v1"
+                )
+
+    def test_explicit_override_replaces_stale_non_blank_launcher_value(self) -> None:
+        with tempfile.TemporaryDirectory() as directory:
+            path = Path(directory) / ".env"
+            path.write_text("OPENAI_MODEL=gpt-5.6-sol\n", encoding="utf-8")
+            with patch.dict(
+                os.environ, {"OPENAI_MODEL": "gpt-5-mini"}, clear=True
+            ):
+                load_local_env(path, override=True)
+                self.assertEqual(os.environ["OPENAI_MODEL"], "gpt-5.6-sol")
+
+
+if __name__ == "__main__":
+    unittest.main()