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/utils/miniPlayerBridge.ts

@@ -0,0 +1,107 @@
+import { getCurrentWindow } from '@tauri-apps/api/window';
+import { listen, emitTo } from '@tauri-apps/api/event';
+import { usePlayerStore } from '../store/playerStore';
+
+export const MINI_WINDOW_LABEL = 'mini';
+
+export interface MiniSyncPayload {
+  track: {
+    id: string;
+    title: string;
+    artist: string;
+    album: string;
+    albumId?: string;
+    artistId?: string;
+    coverArt?: string;
+    duration?: number;
+    starred?: boolean;
+  } | null;
+  isPlaying: boolean;
+  isMobile: false;
+}
+
+export type MiniControlAction =
+  | 'toggle'
+  | 'next'
+  | 'prev'
+  | 'show-main';
+
+function snapshot(): MiniSyncPayload {
+  const s = usePlayerStore.getState();
+  const t = s.currentTrack;
+  return {
+    track: t ? {
+      id: t.id,
+      title: t.title,
+      artist: t.artist,
+      album: t.album,
+      albumId: t.albumId,
+      artistId: t.artistId,
+      coverArt: t.coverArt,
+      duration: t.duration,
+      starred: !!t.starred,
+    } : null,
+    isPlaying: s.isPlaying,
+    isMobile: false,
+  };
+}
+
+/**
+ * Bridge initialised on the main window. Pushes track/state changes to the
+ * mini window whenever they matter, and handles control events coming back
+ * from the mini window.
+ *
+ * Returns a cleanup function.
+ */
+export function initMiniPlayerBridgeOnMain(): () => void {
+  // Only run on the main window
+  if (getCurrentWindow().label !== 'main') return () => {};
+
+  // Push state to the mini window on every relevant store change.
+  let last = '';
+  const push = () => {
+    const payload = snapshot();
+    const key = `${payload.track?.id ?? ''}|${payload.isPlaying}|${payload.track?.starred ?? ''}`;
+    if (key === last) return;
+    last = key;
+    emitTo(MINI_WINDOW_LABEL, 'mini:sync', payload).catch(() => {});
+  };
+
+  const unsub = usePlayerStore.subscribe((state, prev) => {
+    if (state.currentTrack?.id !== prev.currentTrack?.id
+      || state.isPlaying !== prev.isPlaying
+      || state.currentTrack?.starred !== prev.currentTrack?.starred) {
+      push();
+    }
+  });
+
+  // Push an initial snapshot whenever a new mini window announces itself.
+  const readyUnlisten = listen('mini:ready', () => {
+    last = '';
+    push();
+  });
+
+  // Receive control actions from the mini window.
+  const controlUnlisten = listen<MiniControlAction>('mini:control', (e) => {
+    const action = e.payload;
+    const store = usePlayerStore.getState();
+    switch (action) {
+      case 'toggle':   store.togglePlay(); break;
+      case 'next':     store.next(true); break;
+      case 'prev':     store.previous(); break;
+      case 'show-main': {
+        const w = getCurrentWindow();
+        w.unminimize().catch(() => {});
+        w.show().catch(() => {});
+        w.setFocus().catch(() => {});
+        break;
+      }
+    }
+  });
+
+  return () => {
+    unsub();
+    readyUnlisten.then(fn => fn()).catch(() => {});
+    controlUnlisten.then(fn => fn()).catch(() => {});
+  };
+}