fix: drag works from first attempt + size in window header

- ui.tsx: pass min/max opts to useWindowResize (fixes first-drag bug)
- ui.tsx: move live size to top toolbar (left of expand button)
- main.ts: set figma window title with startup size via showUI({title})

src/main.ts

@@ -10,5 +10,5 @@ export default function () {
     figma.ui.resize(width, height)
   })
 
-  showUI({ width: 320, height: 200, themeColors: true })
+  showUI({ width: 320, height: 200, themeColors: true, title: 'AI assistant (MVP) — 320×200' })
 }