phsl / new-api

- Introduced `sanitizePlaygroundInputs` to normalize `max_tokens` input values.
- Updated `loadConfig` to utilize the new sanitization function.
- Replaced `Input` with `InputNumber` for `max_tokens` in `ParameterControl` for better user experience.
- Modified API payload building logic to handle `max_tokens` more robustly.
- Added tests for new helper functions in `playgroundMaxTokens.js` to ensure correct behavior.