feat: add sine scroller and tracker panel hud

Implement Task 10: HUD components for LE BUS demoscene page.
- Scroller.tsx: canvas-2D sine-wave text animation at bottom
- TrackerPanel.tsx: play/mute control panel (top-right)
- modPlayer.ts: interface stubs (ModState, ModPlayer)
- CSS styling for both components appended to style.css

src/App.tsx

@@ -6,6 +6,8 @@ import { Passengers } from './scene/Passengers'
 import { Sky } from './scene/Sky'
 import { Stops } from './scene/stops/Stops'
 import { useRideInput } from './ride/useRideInput'
+import { Scroller } from './hud/Scroller'
+import { TrackerPanel } from './hud/TrackerPanel'
 
 export default function App() {
   useRideInput()
@@ -26,6 +28,8 @@ export default function App() {
         <Sky />
         <Stops />
       </Canvas>
+      <Scroller />
+      <TrackerPanel player={null} />
     </div>
   )
 }

src/audio/modPlayer.ts

@@ -0,0 +1,8 @@
+export type ModState = 'idle' | 'loading' | 'playing' | 'paused' | 'unavailable'
+
+export interface ModPlayer {
+  state: ModState
+  toggle(): Promise<ModState>
+  setMuted(muted: boolean): void
+  onChange(fn: (s: ModState) => void): void
+}

src/hud/Scroller.tsx

@@ -0,0 +1,42 @@
+import { useEffect, useRef } from 'react'
+import { SCROLLER_TEXT } from '../content/greetings'
+
+const CHAR_W = 26
+const SPEED = 2.2
+
+export function Scroller() {
+  const ref = useRef<HTMLCanvasElement>(null)
+  useEffect(() => {
+    const cv = ref.current!
+    const ctx = cv.getContext('2d')!
+    let raf = 0
+    let x = window.innerWidth
+    const resize = () => {
+      cv.width = window.innerWidth
+      cv.height = 72
+    }
+    resize()
+    window.addEventListener('resize', resize)
+    const total = SCROLLER_TEXT.length * CHAR_W
+    const loop = (now: number) => {
+      ctx.clearRect(0, 0, cv.width, cv.height)
+      ctx.font = 'bold 40px "Courier New", monospace'
+      ctx.fillStyle = '#ffd23f'
+      x -= SPEED
+      if (x < -total) x = window.innerWidth
+      for (let i = 0; i < SCROLLER_TEXT.length; i++) {
+        const cx = x + i * CHAR_W
+        if (cx < -CHAR_W || cx > cv.width) continue
+        const cy = 42 + Math.sin(cx * 0.018 + now * 0.004) * 14
+        ctx.fillText(SCROLLER_TEXT[i], cx, cy)
+      }
+      raf = requestAnimationFrame(loop)
+    }
+    raf = requestAnimationFrame(loop)
+    return () => {
+      cancelAnimationFrame(raf)
+      window.removeEventListener('resize', resize)
+    }
+  }, [])
+  return <canvas id="scroller" ref={ref} aria-hidden="true" />
+}

src/hud/TrackerPanel.tsx

@@ -0,0 +1,39 @@
+import { useEffect, useState } from 'react'
+import type { ModPlayer, ModState } from '../audio/modPlayer'
+
+export function TrackerPanel({ player }: { player: ModPlayer | null }) {
+  const [state, setState] = useState<ModState>(player ? player.state : 'unavailable')
+  const [muted, setMuted] = useState(false)
+
+  useEffect(() => {
+    if (player) player.onChange(setState)
+  }, [player])
+
+  const label =
+    state === 'playing' ? '⏸' : state === 'loading' ? '…' : '▶'
+  const status =
+    state === 'unavailable' ? 'NO MOD' : state === 'loading' ? 'LOADING' : 'RIDE.MOD'
+
+  return (
+    <div id="tracker" role="group" aria-label="Musique tracker">
+      <button
+        disabled={!player || state === 'unavailable' || state === 'loading'}
+        onClick={() => player?.toggle()}
+        aria-label="Lecture / pause du module"
+      >
+        {label}
+      </button>
+      <button
+        disabled={!player || state === 'unavailable'}
+        onClick={() => {
+          player?.setMuted(!muted)
+          setMuted(!muted)
+        }}
+        aria-label="Couper le son"
+      >
+        {muted ? '🔇' : '🔊'}
+      </button>
+      <span className="status">{status}</span>
+    </div>
+  )
+}

src/style.css

@@ -64,3 +64,26 @@ body.demo-on #fallback {
 }
 .panel a.sign:hover, .panel button.sign:hover { background: #ffd23f; color: #05010d; }
 .panel ul { margin: 6px 0; padding-left: 18px; font-size: 0.8rem; }
+
+#scroller { position: fixed; left: 0; bottom: 0; width: 100%; height: 72px; pointer-events: none; }
+#tracker {
+  position: fixed;
+  top: 12px;
+  right: 12px;
+  display: flex;
+  gap: 6px;
+  align-items: center;
+  background: rgba(5, 1, 13, 0.85);
+  border: 3px solid #ffd23f;
+  padding: 6px 10px;
+}
+#tracker button {
+  background: none;
+  border: 2px solid #ffd23f;
+  color: #ffd23f;
+  font: inherit;
+  cursor: pointer;
+  min-width: 2.2rem;
+}
+#tracker button:disabled { opacity: 0.4; cursor: default; }
+#tracker .status { font-size: 0.7rem; color: #9be564; }