Complete PR review feedback implementation with clean importlib.resources approach

- Remove redundant path checks between Path("conf/custom_models.json") and Path.cwd() variants
- Implement proper importlib.resources.files('conf') approach for robust packaging
- Create conf/__init__.py to make conf a proper Python package
- Update pyproject.toml to include conf* in package discovery
- Clean up verbose comments and simplify resource loading logic
- Fix test mocking to use correct importlib.resources.files target
- All tests passing (8/8) with proper resource and fallback functionality

Addresses all gemini-code-assist bot feedback from PR #227

pyproject.toml

@@ -12,7 +12,7 @@ dependencies = [
 ]
 
 [tool.setuptools.packages.find]
-include = ["tools*", "providers*", "systemprompts*", "utils*"]
+include = ["tools*", "providers*", "systemprompts*", "utils*", "conf*"]
 
 [tool.setuptools]
 py-modules = ["server", "config"]