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

docs/agent-log.md

@@ -4,6 +4,18 @@ What agents have done, newest first. Add an entry for every piece of work: the d
 note or request it was for, what changed, the files touched, the tests run, and anything left
 open or not verified. Keep each entry short; the git history has the details.
 
+## 2026-10-29: new belts stood still until reload; golden test after t45 (Claude)
+
+- Owner bug: in a world started after a long session, belts built after loading never moved
+  (save and reload fixed them). The 6-tick power rebuild throttle (`nextPowerBuild`) survived
+  the tick reset of a new or loaded world, so rebuilds waited for the old tick count. Now a wait
+  longer than 6 ticks counts as stale. Not caused by t45; tests had hidden it with `nextPowerBuild=0`.
+- t45 animates belts from the tick (`transportClock`), so `t_gpu_golden.py` now pins `tick`
+  (1000 for pixel = old R.frame, 300 for smooth = old 5 s clock); all goldens match exactly again.
+- Files: sim/machine-tick, test/{t_basics.js,t_gpu_golden.py}, this log.
+- Tests: new t_basics check failed before the fix; all headless suites, t_stalls.py,
+  t_gpu_golden.py and play.py pass.
+
 ## 2026-10-29: t103 blow carried liquids without the Flask (Codex)
 
 - Removed only blow-side Flask gates, including Shift's HUD list; corrected the Flask hint.