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/components/MiniPlayer.tsx

@@ -0,0 +1,151 @@
+import React, { useEffect, useRef, useState } from 'react';
+import { emit, listen } from '@tauri-apps/api/event';
+import { invoke } from '@tauri-apps/api/core';
+import { getCurrentWindow } from '@tauri-apps/api/window';
+import { Play, Pause, SkipBack, SkipForward, Pin, PinOff, Maximize2, X } from 'lucide-react';
+import CachedImage from './CachedImage';
+import { buildCoverArtUrl, coverArtCacheKey } from '../api/subsonic';
+import type { MiniSyncPayload, MiniControlAction } from '../utils/miniPlayerBridge';
+
+interface ProgressPayload {
+  current_time: number;
+  duration: number;
+}
+
+function fmt(seconds: number): string {
+  if (!isFinite(seconds) || seconds < 0) seconds = 0;
+  const m = Math.floor(seconds / 60);
+  const s = Math.floor(seconds % 60);
+  return `${m}:${s.toString().padStart(2, '0')}`;
+}
+
+export default function MiniPlayer() {
+  const [state, setState] = useState<MiniSyncPayload>({ track: null, isPlaying: false, isMobile: false });
+  const [currentTime, setCurrentTime] = useState(0);
+  const [duration, setDuration] = useState(0);
+  const [alwaysOnTop, setAlwaysOnTop] = useState(true);
+  const ticker = useRef<number | null>(null);
+
+  // Announce to main window that we're mounted; it replies with a snapshot.
+  useEffect(() => {
+    emit('mini:ready', {}).catch(() => {});
+  }, []);
+
+  // Keyboard: Space → toggle, ← / → → prev / next. Ignore when typing.
+  useEffect(() => {
+    const onKey = (e: KeyboardEvent) => {
+      const tgt = e.target as HTMLElement | null;
+      const tag = tgt?.tagName;
+      if (tag === 'INPUT' || tag === 'TEXTAREA' || tgt?.isContentEditable) return;
+      if (e.key === ' ' || e.code === 'Space') {
+        e.preventDefault();
+        emit('mini:control', 'toggle').catch(() => {});
+      } else if (e.key === 'ArrowRight') {
+        emit('mini:control', 'next').catch(() => {});
+      } else if (e.key === 'ArrowLeft') {
+        emit('mini:control', 'prev').catch(() => {});
+      }
+    };
+    window.addEventListener('keydown', onKey);
+    return () => window.removeEventListener('keydown', onKey);
+  }, []);
+
+  // Subscribe to state + progress from the main window / Rust.
+  useEffect(() => {
+    const unSync = listen<MiniSyncPayload>('mini:sync', (e) => {
+      setState(e.payload);
+      if (e.payload.track?.duration) setDuration(e.payload.track.duration);
+    });
+    const unProgress = listen<ProgressPayload>('audio:progress', (e) => {
+      setCurrentTime(e.payload.current_time);
+      if (e.payload.duration > 0) setDuration(e.payload.duration);
+    });
+    const unEnded = listen('audio:ended', () => setCurrentTime(0));
+    return () => {
+      unSync.then(fn => fn()).catch(() => {});
+      unProgress.then(fn => fn()).catch(() => {});
+      unEnded.then(fn => fn()).catch(() => {});
+      if (ticker.current) window.clearInterval(ticker.current);
+    };
+  }, []);
+
+  const control = (action: MiniControlAction) => emit('mini:control', action).catch(() => {});
+
+  const toggleOnTop = async () => {
+    const next = !alwaysOnTop;
+    setAlwaysOnTop(next);
+    try { await invoke('set_mini_player_always_on_top', { onTop: next }); } catch {}
+  };
+
+  const closeMini = async () => {
+    try { await invoke('close_mini_player'); } catch {}
+  };
+
+  const showMain = () => invoke('show_main_window').catch(() => {});
+
+  const { track, isPlaying } = state;
+  const progress = duration > 0 ? Math.min(100, (currentTime / duration) * 100) : 0;
+
+  return (
+    <div className="mini-player">
+      <div className="mini-player__art">
+        {track?.coverArt ? (
+          <CachedImage
+            src={buildCoverArtUrl(track.coverArt, 300)}
+            cacheKey={coverArtCacheKey(track.coverArt, 300)}
+            alt={track.album}
+          />
+        ) : (
+          <div className="mini-player__art-fallback" />
+        )}
+      </div>
+
+      <div className="mini-player__body">
+        <div className="mini-player__titles">
+          <div className="mini-player__title" title={track?.title}>
+            {track?.title ?? '—'}
+          </div>
+          <div className="mini-player__artist" title={track?.artist}>
+            {track?.artist ?? ''}
+          </div>
+        </div>
+
+        <div className="mini-player__controls">
+          <button className="mini-player__btn" onClick={() => control('prev')} data-tauri-drag-region="false">
+            <SkipBack size={16} />
+          </button>
+          <button className="mini-player__btn mini-player__btn--primary" onClick={() => control('toggle')}>
+            {isPlaying ? <Pause size={18} /> : <Play size={18} />}
+          </button>
+          <button className="mini-player__btn" onClick={() => control('next')}>
+            <SkipForward size={16} />
+          </button>
+        </div>
+
+        <div className="mini-player__progress">
+          <div className="mini-player__progress-time">{fmt(currentTime)}</div>
+          <div className="mini-player__progress-track">
+            <div className="mini-player__progress-fill" style={{ width: `${progress}%` }} />
+          </div>
+          <div className="mini-player__progress-time">{fmt(duration)}</div>
+        </div>
+      </div>
+
+      <div className="mini-player__toolbar">
+        <button
+          className={`mini-player__tool${alwaysOnTop ? ' mini-player__tool--active' : ''}`}
+          onClick={toggleOnTop}
+          data-tooltip={alwaysOnTop ? 'Pin off' : 'Pin on top'}
+        >
+          {alwaysOnTop ? <Pin size={13} /> : <PinOff size={13} />}
+        </button>
+        <button className="mini-player__tool" onClick={showMain} data-tooltip="Open main window">
+          <Maximize2 size={13} />
+        </button>
+        <button className="mini-player__tool" onClick={closeMini} data-tooltip="Close">
+          <X size={13} />
+        </button>
+      </div>
+    </div>
+  );
+}