Spec fixes come from a test where pi + deepseek-v4.1-flash wrote effects
from EFFECTS.md alone: glitch-blocks and ghost-stamps both compiled on the
first try. The agent's feedback led to in.dt (frame time), documented
limits of in.prev as memory, and a --check warning for ignored slider lines.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
