feat: Complete Unity/game engine support and local source type validation

Completes the implementation for Unity/Unreal/Godot game engine support
and adds missing "local" source type validation.

Changes:
- Add "local" to VALID_SOURCE_TYPES in config_validator.py
- Add _validate_local_source() method with full validation
- Add Unity/Unreal/Godot to FRAMEWORK_MARKERS for priority detection
- Add game engine directory exclusions to all 3 scrapers:
  * Unity: Library/, Temp/, Logs/, UserSettings/, etc.
  * Unreal: Intermediate/, Saved/, DerivedDataCache/
  * Godot: .godot/, .import/
- Prevents scanning massive build cache directories (saves GBs + hours)

This completes all features mentioned in PR #278:
✅ Unity/Unreal/Godot framework detection with priority
✅ Pattern enhancement performance fix (grouped approach)
✅ Game engine directory exclusions
✅ Phase 5 SKILL.md AI enhancement
✅ Local source references copying
✅ "local" source type validation
✅ Config field name compatibility
✅ C# test example extraction

Tested:
- All unified config tests pass (18/18)
- All config validation tests pass (28/28)
- Ready for Unity project testing

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/skill_seekers/cli/config_extractor.py

@@ -222,6 +222,7 @@ class ConfigFileDetector:
 
     # Directories to skip
     SKIP_DIRS = {
+        # Python/Node
         "node_modules",
         "venv",
         "env",
@@ -237,6 +238,23 @@ class ConfigFileDetector:
         "coverage",
         ".eggs",
         "*.egg-info",
+        # Unity (critical - contains massive build cache)
+        "Library",
+        "Temp",
+        "Logs",
+        "UserSettings",
+        "MemoryCaptures",
+        "Recordings",
+        # Unreal Engine
+        "Intermediate",
+        "Saved",
+        "DerivedDataCache",
+        # Godot
+        ".godot",
+        ".import",
+        # Misc
+        "tmp",
+        ".tmp",
     }
 
     def find_config_files(self, directory: Path, max_files: int = 100) -> list[ConfigFile]: