feat(mini-player): floating mini window — early alpha (#162)

A second webview window (label "mini") with a compact player: album art,
title, artist, prev/play/next, progress bar, pin-on-top toggle, expand
back to main, close. Main minimizes on open and restores when the mini
is hidden or closed. Spacebar toggles, arrow keys skip tracks.

Cross-window sync: main window subscribes to playerStore and pushes
`mini:sync` via emitTo on track / play-state change. Audio progress
already broadcasts to all windows via `audio:progress`. Control actions
(prev/next/toggle) come back via `mini:control`; main-window restore
goes through a direct Rust command because WebKitGTK pauses JS in a
minimized webview.

Tiling-WM detection reused from existing `is_tiling_wm()` — always-on-top
is skipped on Hyprland/Sway/i3 since it's ignored there anyway.

Early alpha: no queue expand, no lyrics, no EQ, no drag-snap. Scope kept
deliberately tight for v1; follow-ups planned.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/main.tsx

@@ -1,11 +1,20 @@
 import { StrictMode } from 'react';
 import ReactDOM from 'react-dom/client';
+import { getCurrentWindow } from '@tauri-apps/api/window';
 import App from './App';
 import './i18n';
 import './styles/theme.css';
 import './styles/layout.css';
 import './styles/components.css';
 
+// Expose the Tauri window label synchronously so App() can pick its root
+// component (main app vs mini player) on first render without flicker.
+try {
+  (window as any).__PSY_WINDOW_LABEL__ = getCurrentWindow().label;
+} catch {
+  (window as any).__PSY_WINDOW_LABEL__ = 'main';
+}
+
 ReactDOM.createRoot(document.getElementById('root')!).render(
   <StrictMode>
     <App />