feat: add ComfyUI-style prompt weighting via compel

- Support (word:weight), [word], ((nested)) syntax
- Support BREAK for conditioning chunking (.and() translation)
- Use CompelForSDXL (modern API, avoids deprecation)
- Add --raw flag to bypass weighting and fall back to plain encoding
- Update README with Prompt Syntax section and examples
- Add docs/comfyui-prompt-style.md with design doc

pyproject.toml

@@ -15,6 +15,7 @@ dependencies = [
     "pillow",
     "pyyaml",
     "click",
+    "compel",
 ]
 
 [tool.setuptools.packages.find]