* fix(ui): add anyOf/oneOf support in config form
- Handle literal unions as dropdowns with type preservation
- Handle primitive unions (string|number, boolean|string) as text inputs
- Unwrap single-variant optional types
- Fix enum handler to preserve types via index-based values
- Update normalizeUnion to support primitive unions in schema analysis
- Exclude allOf from union normalization (stays unsupported)
Fields like Thinking Default, Allow From, Memory now render properly
instead of showing 'unsupported schema node' errors.
* UI: fix enum placeholder collision
* Docs: update changelog for PR #268
---------
Co-authored-by: Shadow <hi@shadowing.dev>