Add comprehensive tests for ast-grep and tree-sitter relationship extraction

- Introduced test suite for AstGrepPythonProcessor covering pattern definitions, parsing, and relationship extraction.
- Added comparison tests between tree-sitter and ast-grep for consistency in relationship extraction.
- Implemented tests for ast-grep binding module to verify functionality and availability.
- Ensured tests cover various scenarios including inheritance, function calls, and imports.

codex-lens/src/codexlens/config.py

@@ -189,6 +189,9 @@ class Config:
     api_batch_size_max: int = 2048  # Absolute upper limit for batch size
     chars_per_token_estimate: int = 4  # Characters per token estimation ratio
 
+    # Parser configuration
+    use_astgrep: bool = False  # Use ast-grep for Python relationship extraction (tree-sitter is default)
+
     def __post_init__(self) -> None:
         try:
             self.data_dir = self.data_dir.expanduser().resolve()