fix: correct ty configuration field name

Change 'search_path' to 'src' in [tool.ty] configuration.
The ty type checker expects 'src' as the field name, not 'search_path'.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: dguido

{{cookiecutter.project_slug}}/pyproject.toml

@@ -61,7 +61,7 @@ omit = ["{{ cookiecutter.__project_src_path }}/_cli.py"]
 
 [tool.ty]
 # Astral's experimental type checker
-search_path = ["src"]
+src = ["src"]
 
 [tool.ruff]
 line-length = 100