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/schemas/settings.ts

@@ -12,6 +12,7 @@ export const settingsSchema = z.object({
   showInTray: z.boolean(),
   minimizeToTrayOnClose: z.boolean(),
   enableClaudePluginIntegration: z.boolean().optional(),
+  skipClaudeOnboarding: z.boolean().optional(),
   launchOnStartup: z.boolean().optional(),
   language: z.enum(["en", "zh", "ja"]).optional(),