Ambient WebGL petals + cute notification sounds

Add a fixed, GPU-driven petal layer that drifts soft blossoms over the
page (sparse, translucent, paused when hidden, skipped under
prefers-reduced-motion). Add a synthesized cute sound palette — bubble
pop, water droplet, soft bell, sparkle, cheer — generated as embedded
WAV assets (scripts/gen_sounds.py) and played through a quiet Web Audio
bus with soft-clipping and a persisted mute toggle in the status bar.

Sounds fire per suggestion type when fresh advice arrives (staggered,
old pending advice stays silent) and on companion bubbles by tone.

Claude-Session: https://claude.ai/code/session_016Yr6jELuRc7hyzYLccQKZd

web/src/components/StatusBar/StatusBar.tsx

@@ -1,6 +1,7 @@
 import { useEffect, useRef, useState } from 'react'
 import type { SaveStatus } from '../../hooks/useAutoSave'
 import { StatsPanel } from './StatsPanel'
+import { SoundToggle } from './SoundToggle'
 
 interface Props {
   wordCount: number
@@ -120,6 +121,9 @@ export function StatusBar({ wordCount, text, saveStatus, checking, voicing, llmD
           </span>
         </>
       )}
+      <div className="ml-auto">
+        <SoundToggle />
+      </div>
     </footer>
   )
 }