Multi-core simulation: grain movement and heat across a worker pool (t88 phase 3)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

test/t_gpu_golden.py

@@ -1,5 +1,5 @@
 """Frozen legacy references, captured before retirement; compare the WebGPU world only."""
-import base64, pathlib, sys, subprocess
+import base64, gzip, json, pathlib, sys, subprocess
 sys.path.insert(0, str(pathlib.Path(__file__).resolve().parent.parent / 'tools'))
 from use_venv import ensure_playwright; ensure_playwright()
 from browser import launch, consume_gpu_option
@@ -16,7 +16,17 @@ with launch(viewport={'width': 640, 'height': 480}) as (_, pg, url):
     for scene in ['renderer','joins','sky','lamp','opening','magma','fire']:
         for look in ['pixel','smooth']:
             for zoom in [12,2]:
-                pg.evaluate('(h)=>{generateWorld(424242,640,h,null);enterGame();GAME.paused=true;}',512 if scene=='joins' else 384)
+                height = 512 if scene=='joins' else 384
+                frozen = json.loads(gzip.decompress((ROOT/f'test/fixtures/golden-world-640x{height}.json.gz').read_bytes()))
+                # Keep the inputs that produced the legacy PNGs when simulation RNG changes.
+                pg.evaluate("""([h, frozen])=>{
+                  generateWorld(424242,640,h,null);
+                  for(const [name,encoded]of Object.entries(frozen)) {
+                    const target=eval(name),raw=Uint8Array.from(atob(encoded),c=>c.charCodeAt(0));
+                    new Uint8Array(target.buffer).set(raw);
+                  }
+                  enterGame();GAME.paused=true;
+                }""",[height,frozen])
                 name = 'joins' if scene=='joins' else 't88-renderer' if scene in ['renderer','sky'] else 't88-light'
                 pg.evaluate('() => {'+(ROOT / f'tools/scenes/{name}.js').read_text()+'}')
                 if scene not in ['renderer','joins','sky']: