feat: add native Svelte UI for robot recording, teleop, and eval

Adds a generic web dashboard at ui/ that works with any robot/teleop
type in lerobot. Calls lerobot-record, lerobot-teleoperate, and
lerobot-eval as background subprocesses.

Features:
- Setup tab: robot type/port/id, dynamic camera configuration
- Record tab: dataset config, teleop device, start/stop recording
- Teleop tab: start/stop teleoperation
- Evaluate tab: policy path, env type, device config
- Live MJPEG camera preview (paused during subprocess, auto-restarts)
- Terminal-style log panel streaming subprocess stdout/stderr
- Hardware discovery: serial ports, CAN interfaces, OpenCV cameras
- Config persistence via localStorage
- Dark theme, responsive camera grid

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

ui/package.json

@@ -0,0 +1,15 @@
+{
+  "name": "lerobot-ui",
+  "version": "1.0.0",
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "vite build",
+    "preview": "vite preview"
+  },
+  "devDependencies": {
+    "@sveltejs/vite-plugin-svelte": "^3.0.0",
+    "svelte": "^4.2.0",
+    "vite": "^5.0.0"
+  }
+}