feat: add Claude common config snippet functionality

- Create useCommonConfigSnippet hook to manage common config state
- Create CommonConfigEditor component with modal for editing
- Support merging/removing common config snippets from provider configs
- Persist common config to localStorage for reuse across providers
- Auto-detect if provider config contains common snippet
- Replace JSON editor with CommonConfigEditor in ProviderForm

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

@@ -7,3 +7,4 @@ export { useApiKeyLink } from "./useApiKeyLink";
 export { useCustomEndpoints } from "./useCustomEndpoints";
 export { useKimiModelSelector } from "./useKimiModelSelector";
 export { useTemplateValues } from "./useTemplateValues";
+export { useCommonConfigSnippet } from "./useCommonConfigSnippet";