fix: KAPLAY scene init robustness — wait for layout, catch errors

- FightViewer: wrap createFightScene in try/catch so scene failures
  don't crash every subsequent playRound call
- FightViewer: wait for container to have non-zero dimensions before
  creating canvas (prevents 0x0 canvas causing sprite load failures)
- FightViewer: graceful log-only fallback when scene init fails
- FightPage: same dimension-wait and try/catch for initLiveScene
- Fallback canvas dimensions (800x500) when container not yet laid out

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

frontend/src/components/FightViewer.vue

@@ -112,12 +112,17 @@ async function initScene() {
   const container = canvasContainer.value
   if (!container) return
 
+  // Wait for container to have dimensions (layout may not be complete yet)
+  for (let i = 0; i < 10 && (!container.clientWidth || !container.clientHeight); i++) {
+    await new Promise(r => requestAnimationFrame(r))
+  }
+
   // Replace canvas element so Kaplay gets a fresh context
   const oldCanvas = canvasRef.value
   const newCanvas = document.createElement('canvas')
   newCanvas.className = 'w-full h-full block'
-  newCanvas.width = container.clientWidth
-  newCanvas.height = container.clientHeight
+  newCanvas.width = container.clientWidth || 800
+  newCanvas.height = container.clientHeight || 500
   if (oldCanvas) {
     oldCanvas.replaceWith(newCanvas)
   } else {