Three independent bugs were stacking to make ui/viz.html unusable from `main`:
1. Three.js r160 removed `examples/js/OrbitControls.js`, so the script-tag
load 404'd and `new THREE.OrbitControls(...)` threw. Switch to an
importmap that pulls the ES module build, then re-expose
`window.THREE` and `THREE.OrbitControls` so the existing component
modules (scene.js, body-model.js, …) keep working without a wider
refactor.
2. The WebSocket client was hardcoded to `ws://localhost:8000/ws/pose`,
but the sensing-server listens on `--ws-port` (8765 default, 3001 in
the Docker image) at `/ws/sensing`. Reuse the existing
`buildSensingWsUrl()` helper from `sensing.service.js` so port
pairings are handled centrally, and add a `?ws=…` query-string
override for non-standard setups. The websocket-client.js default is
also updated to derive from `window.location` instead of the dead
`:8000/ws/pose` literal.
3. `ToastManager.show()` called `this.container.appendChild(...)` even
when `init()` had never been called, throwing a TypeError that
killed the rest of page initialization. Auto-init the container
lazily on first show (patch from issue reporter).
Closes#760.
Co-Authored-By: claude-flow <ruv@ruv.net>
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