Belts built after a tick reset join the network; pin tick in golden renders

A world started after a long session kept the old nextPowerBuild, so new
belts were never added until a reload. Treat a wait longer than 6 ticks as
stale. The golden test pins tick now that t45 animates belts from it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Cj2RPXdPykKMEz5BXXczsj

test/t_gpu_golden.py

@@ -39,7 +39,8 @@ with launch(viewport={'width': 640, 'height': 480}) as (_, pg, url):
                   SET.look=look;SET.zoom=zoom;SET.lighting='full';SET.lightEvery=1;SET.glow='low';
                   SM.t0=0; SM.surf=-1;
                   performance.now=()=>5000;resizeRender();bot.x=CAM[0]-bot.w/2;bot.y=CAM[1]-bot.h/2;
-                  snapCamera();R.frame=1000;drawWorld();
+                  // belts animate from the tick: pixel look by tick (was R.frame), smooth by tick/60 s (was the 5 s clock)
+                  snapCamera();R.frame=1000;tick=look==='smooth'?300:1000;drawWorld();
                 }""",[look,zoom])
                 raw=pg.evaluate("""() => {
                   const c=document.createElement('canvas');c.width=384;c.height=288;