fix: E2E test fixes and host resilience improvements (#206)

1. video-resource-server: Add missing server-utils.ts and fix import path
   - Was importing from non-existent ../shared/server-utils.js
   - Now correctly imports from ./src/server-utils.js

2. basic-host: Be resilient to individual server connection failures
   - Use Promise.allSettled instead of Promise.all
   - Failed connections are logged as warnings but don't crash the UI
   - Only throws if ALL servers fail to connect

3. threejs-server: Add id to canvas for reliable screenshot masking
   - Added id="threejs-canvas" to the canvas element
   - Updated e2e test masks to use #threejs-canvas and .threejs-container
   - Fixes flaky Three.js screenshot comparisons in CI

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <noreply@anthropic.com>

examples/threejs-server/src/threejs-app.tsx

@@ -188,6 +188,7 @@ export default function ThreeJSApp({
       style={containerStyle}
     >
       <canvas
+        id="threejs-canvas"
         ref={canvasRef}
         style={{
           width: "100%",