feat(settings): add option to skip Claude Code first-run confirmation

Add a new setting to automatically skip Claude Code's onboarding screen
by writing hasCompletedOnboarding=true to ~/.claude.json. The setting
defaults to enabled for better user experience.

- Add set/clear_has_completed_onboarding functions in claude_mcp.rs
- Add Tauri commands and frontend API integration
- Add toggle in WindowSettings with i18n support (en/zh/ja)
- Fix hardcoded Chinese text in tests to use i18n keys

src/lib/api/settings.ts

@@ -69,6 +69,14 @@ export const settingsApi = {
     return await invoke("apply_claude_plugin_config", { official });
   },
 
+  async applyClaudeOnboardingSkip(): Promise<boolean> {
+    return await invoke("apply_claude_onboarding_skip");
+  },
+
+  async clearClaudeOnboardingSkip(): Promise<boolean> {
+    return await invoke("clear_claude_onboarding_skip");
+  },
+
   async saveFileDialog(defaultName: string): Promise<string | null> {
     return await invoke("save_file_dialog", { defaultName });
   },