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/Companion/useCompanion.ts

@@ -12,6 +12,7 @@ import {
   type Line,
 } from './tips'
 import { analyzeProse } from './prose'
+import { playSound } from '../../audio/sounds'
 
 // The kitten's expression. Maps to a Lottie animation when assets are present,
 // otherwise to an emoji placeholder (see PetalCompanion).
@@ -95,6 +96,11 @@ export function useCompanion({ wordCount, saveStatus, editTick, acceptTick, text
       lastProactive.current = t
     }
     sleeping.current = false
+    // A soft sound to match the bubble's mood — celebrations cheer, gentle
+    // cheers sparkle, break nudges chime, and tips give a little bubble pop.
+    playSound(
+      opts?.celebrate ? 'cheer' : b.tone === 'cheer' ? 'shimmer' : b.tone === 'break' ? 'chime' : 'pop',
+    )
     setBubble(b)
     setMood(opts?.celebrate ? 'celebrate' : 'talking')
     clearTimeout(bubbleTimer.current)