zen: calmer UB — live speed control (default 0.7×) + a touch bigger (scale 1.2)

Swim1_norm read a bit restless; add a tunable playback speed (default 0.7× for a calm
glide, ×0.7 again under reduced-motion) wired into the render tuner, and bump the default
scale to 1.2 for more presence. Both live-adjustable at /zen?debug=1.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/lib/zen/aquarium.js

@@ -26,7 +26,8 @@ const MODEL_URL = '/models/ub-angelfish.glb';
 export const DEFAULTS = {
   yaw: Math.PI / 2,          // ub.rotation.y — side-on-ish (tune live; head faces ±Z)
   pitch: 0,                  // ub.rotation.x — nose up/down
-  scale: 1,                  // multiplier on the auto-fit size
+  scale: 1.2,                // multiplier on the auto-fit size (a touch bigger = more presence)
+  speed: 0.7,                // swim playback rate — <1 = calmer glide
   finTranslucent: false,     // false = opaque alpha-tested (coherent); true = blended
   finSide: 'double',         // front | back | double (fins are thin → double reads fuller)
   finOpacity: 0.9,           // only when translucent
@@ -124,7 +125,8 @@ export async function createAquarium(canvas, initial = {}) {
   const baseClip = mixer.clipAction(gltf.animations[0]);   // the trimmed swim loop
   baseClip.play();
   const baseDuration = baseClip.getClip().duration || 1;
-  mixer.timeScale = reduced ? 0.6 : 1;   // calmer when reduced-motion
+  const applySpeed = () => { mixer.timeScale = (params.speed ?? 0.7) * (reduced ? 0.7 : 1); };
+  applySpeed();   // calm glide by default; extra-calm under reduced-motion
 
   resize();
   // The canvas lives in a responsive container; a ResizeObserver catches layout
@@ -153,6 +155,7 @@ export async function createAquarium(canvas, initial = {}) {
       Object.assign(params, next);
       applyMaterials();
       applyTransform();
+      applySpeed();
       return { ...params };
     },
     getParams() { return { ...params }; },

frontend/src/routes/zen/+page.svelte

@@ -95,6 +95,8 @@
         <input type="range" min="-0.6" max="0.6" step="0.01" bind:value={dbg.pitch} oninput={apply} /></label>
       <label>scale <span>{dbg.scale.toFixed(2)}</span>
         <input type="range" min="0.3" max="2.5" step="0.05" bind:value={dbg.scale} oninput={apply} /></label>
+      <label>speed <span>{dbg.speed.toFixed(2)}</span>
+        <input type="range" min="0.2" max="1.5" step="0.05" bind:value={dbg.speed} oninput={apply} /></label>
 
       <hr />
       <div class="ph">Fins &amp; tail</div>