fix: isomorphic xstate imports + singleplayer worker boot

- TickSystem, ReconnectManager: replace bare 'xstate' static import with
  top-level await dynamic import using _isNode guard — Chrome 145 workers
  do not inherit page importmaps, causing bare specifier resolution to fail
- XRWidgets: fix updateFade() to use _fadeActor.getSnapshot().value instead
  of undefined fadeState variable
- server.js: fix stale watcher for client/animation.js → AnimationStateMachine
  + AnimationLibrary
- draco: add missing draco_wasm_wrapper.js and draco_encoder.js files

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: lanmower

client/XRWidgets.js

@@ -155,8 +155,9 @@ export function createXRWidgets(renderer, scene, camera, vrSettings) {
 
   function updateFade(dt) {
     if (!fadeQuad) { const q = new THREE.Mesh(new THREE.PlaneGeometry(2, 2), new THREE.MeshBasicMaterial({ color: 0x000000, transparent: true, opacity: 0, depthTest: false, depthWrite: false })); q.renderOrder = 9999; fadeQuad = q; camera.add(fadeQuad); fadeQuad.position.z = -0.1 }
-    if (fadeState === 'in') { fadeOpacity += FADE_SPEED * dt; if (fadeOpacity >= 1) { fadeOpacity = 1; fadeState = 'delay'; setTimeout(() => { fadeState = 'out' }, FADE_DELAY) } }
-    else if (fadeState === 'out') { fadeOpacity -= FADE_SPEED * dt; if (fadeOpacity <= 0) { fadeOpacity = 0; fadeState = 'none' } }
+    const fs = _fadeActor.getSnapshot().value
+    if (fs === 'fadeIn') { fadeOpacity += FADE_SPEED * dt; if (fadeOpacity >= 1) { fadeOpacity = 1; _fadeActor.send({ type: 'FULL' }); setTimeout(() => _fadeActor.send({ type: 'RESUME' }), FADE_DELAY) } }
+    else if (fs === 'fadeOut') { fadeOpacity -= FADE_SPEED * dt; if (fadeOpacity <= 0) { fadeOpacity = 0; _fadeActor.send({ type: 'DONE' }) } }
     fadeQuad.material.opacity = fadeOpacity; fadeQuad.visible = fadeOpacity > 0.01
   }