feat: add real-time TOML validation for Codex config

- Add smol-toml dependency for client-side TOML parsing
- Create useCodexTomlValidation hook with 500ms debounce
- Display validation errors below config.toml textarea
- Trigger validation on onChange for immediate user feedback
- Backend validation remains as fallback for data integrity

src/components/providers/forms/hooks/index.ts

@@ -10,3 +10,4 @@ export { useTemplateValues } from "./useTemplateValues";
 export { useCommonConfigSnippet } from "./useCommonConfigSnippet";
 export { useCodexCommonConfig } from "./useCodexCommonConfig";
 export { useSpeedTestEndpoints } from "./useSpeedTestEndpoints";
+export { useCodexTomlValidation } from "./useCodexTomlValidation";