fix: refine docked host compatibility handling

[JS-banana]

Summary

• prevent Windows docked hosts from staying visible while dialogs/settings are open
• apply Grok/X-specific webview compatibility handling and remove Windows docked host shadow artifacts
• exit directly on Windows close while preserving non-Windows hide-to-tray behavior

Test Plan

• pnpm vitest run tests/unit/app-layout.test.tsx tests/unit/app-store.test.ts
• cargo test
• pnpm build