test(15-01): add failing test for enable_semantic_segmentation field

- Test KBSettings has enable_semantic_segmentation field with bool type
- Test default value is True
- Test environment variable override (KB_ENABLE_SEMANTIC_SEGMENTATION)
- Test boolean string parsing (true/false, yes/no, 1/0)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/test_pipeline/test_config.py

@@ -148,3 +148,69 @@ class TestKBSettingsEnvFile:
     def test_kbsettings_model_config_ignores_extra(self):
         """Test KBSettings model_config ignores extra fields"""
         assert KBSettings.model_config.get("extra") == "ignore"
+
+
+class TestEnableSemanticSegmentationField:
+    """Tests for enable_semantic_segmentation field (CONFIG-01)"""
+
+    def test_kbsettings_has_enable_semantic_segmentation_field(self):
+        """Test KBSettings has enable_semantic_segmentation field"""
+        settings = KBSettings(
+            base_path="/tmp/kb",
+            archive_path="/tmp/archive"
+        )
+        assert hasattr(settings, "enable_semantic_segmentation"), \
+            "KBSettings should have enable_semantic_segmentation field"
+        assert isinstance(settings.enable_semantic_segmentation, bool), \
+            "enable_semantic_segmentation should be bool type"
+
+    def test_enable_semantic_segmentation_default_value(self):
+        """Test default value is True"""
+        with patch.dict(os.environ, {}, clear=True):
+            settings = KBSettings(
+                base_path="/tmp/kb",
+                archive_path="/tmp/archive",
+                _env_file=None
+            )
+            assert settings.enable_semantic_segmentation is True, \
+                "enable_semantic_segmentation should default to True"
+
+    def test_enable_semantic_segmentation_from_env(self):
+        """Test KB_ENABLE_SEMANTIC_SEGMENTATION env var is respected"""
+        with patch.dict(os.environ, {
+            "KB_ENABLE_SEMANTIC_SEGMENTATION": "false"
+        }, clear=False):
+            get_settings.cache_clear()
+            settings = KBSettings(
+                base_path="/tmp/kb",
+                archive_path="/tmp/archive"
+            )
+            assert settings.enable_semantic_segmentation is False, \
+                "enable_semantic_segmentation should be False when env var is 'false'"
+
+    def test_enable_semantic_segmentation_boolean_parsing(self):
+        """Test boolean string parsing (true/false, yes/no, 1/0)"""
+        test_cases = [
+            ("true", True),
+            ("True", True),
+            ("TRUE", True),
+            ("yes", True),
+            ("1", True),
+            ("false", False),
+            ("False", False),
+            ("FALSE", False),
+            ("no", False),
+            ("0", False),
+        ]
+
+        for env_value, expected in test_cases:
+            with patch.dict(os.environ, {
+                "KB_ENABLE_SEMANTIC_SEGMENTATION": env_value
+            }, clear=False):
+                get_settings.cache_clear()
+                settings = KBSettings(
+                    base_path="/tmp/kb",
+                    archive_path="/tmp/archive"
+                )
+                assert settings.enable_semantic_segmentation is expected, \
+                    f"Failed for env_value={env_value}, expected={expected}"