Fix CI test, bump to 0.5.7

- test_nested_functions: guard syntax_valid assert behind
  is_tree_sitter_available() (CI doesn't have tree-sitter)
- Bump version to 0.5.7

headroom/__init__.py

@@ -153,7 +153,7 @@ from .transforms import (
     TransformPipeline,
 )
 
-__version__ = "0.5.6"
+__version__ = "0.5.7"
 
 __all__ = [
     # Main client

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "headroom-ai"
-version = "0.5.6"
+version = "0.5.7"
 description = "The Context Optimization Layer for LLM Applications - Cut costs by 50-90%"
 readme = "README.md"
 license = "Apache-2.0"

tests/test_transforms/test_code_compressor.py

@@ -645,7 +645,9 @@ def outer():
         result = compressor.compress(code)
 
         assert result is not None
-        assert result.syntax_valid is True
+        # syntax_valid requires tree-sitter; without it, validation is skipped
+        if is_tree_sitter_available():
+            assert result.syntax_valid is True
 
     def test_syntax_errors_in_input(self, default_config):
         """Syntax errors in input don't crash the compressor."""