fix(play): scene image renders as 1px sliver while CDN bytes still arrive

When the Runware CDN download was slow (~10-20s over VPN / strict
networks, vs. the optimistic <2s the existing comment assumed), the
preload's 8s timeout fired and setImageUrl committed before the bytes
were actually decoded. The rendered <img> has w-auto h-auto and no
intrinsic aspect-ratio source — until the image loads the layout
collapses to roughly 1px tall, giving the "等了很久 → 一根线 → 突然
出图" jank.

Two compounding fixes:

  app/play/page.tsx       IMAGE_PRELOAD_TIMEOUT_MS  8000 → 20000.
                          Real CDN+decode usually finishes well before
                          this; pushing the ceiling out just stops the
                          window where we commit a half-loaded URL.

  components/PlayCanvas.tsx  Add width={1792} height={1024} HTML attrs
                          to the scene <img>. Doesn't affect rendered
                          size (still driven by w-auto h-auto and the
                          maxWidth/maxHeight in sizeStyle); the
                          browser uses them purely as an intrinsic
                          aspect-ratio source, so the placeholder box
                          reserves a 16:9-ish frame even mid-download.

Together: slow networks now mostly wait through preload; on the rare
genuine timeout the layout still holds shape instead of collapsing.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/play/page.tsx

@@ -30,10 +30,14 @@ import type {
 const MUTED_STORAGE_KEY = "infiplot:muted";
 
 // Cap how long we wait for the browser to download + decode a scene image
-// before giving up and rendering anyway. Runware's CDN is normally <2s for a
-// 1792×1024 PNG; tolerate up to 8s before the typewriter starts so a slow
-// download can't strand the player on a blank screen forever.
-const IMAGE_PRELOAD_TIMEOUT_MS = 8000;
+// before giving up and rendering anyway. Runware's CDN is usually <2s for a
+// 1792×1024 PNG, but over slow links / VPN / strict corp networks the same
+// download can stretch to 10-20s. The previous 8s ceiling fired in that
+// window, and because the rendered <img> has no aspect-ratio occupation, the
+// layout collapsed to a one-pixel-tall sliver until the bytes actually
+// finished arriving — "等了很久 → 一根线 → 突然出图" of the original report.
+// 20s + the <img> aspect-video fallback together remove that failure mode.
+const IMAGE_PRELOAD_TIMEOUT_MS = 20000;
 
 // ──────────────────────────────────────────────────────────────────────
 //  Image preload — decode the Runware URL in memory before committing to