[vaprdev]

Summary

Slowly moving creatures jumped several sub-pixels at a time, because every cell held its old split until the new one fit clearly better. Cells under what moved this frame now take a one-sub-pixel step as soon as it fits a little better, so motion glides; bigger changes, steps back, and every still cell keep the full hysteresis.

 tolerance(best, previous, older, moving)
-  bestErr * 1.35 + margin
+  moving cell, one-sub-pixel step, not back to the split before → bestErr * 1.05 + margin * 0.3
+  otherwise                                                    → bestErr * 1.35 + margin

moving comes from dirty-cells' touched boxes (this branch's own copy of the interface is dropped), ignoring tiny boxes and boxes over 10% of the screen. A fit made while something moved is not reused next frame, so dirty refits still match a full refit. --verify-dirty now also fails on any pixel a scene draws outside its touched boxes.

Evidence

Glyph changes on a moving creature through the engine (60 s, octants), origin/main → this branch:

	one-sub-pixel steps	sub-pixels per change
tundra penguins	64% → 75%	1.55 → 1.39
farm cow	52% → 72%	1.66 → 1.41

Worst flicker in dev/check.ts 78 → 83 cells (ocean teeming night; limit 150).

Verified: typecheck, build, dev/check.ts --max-ms=60 in octant and quadrant mode (0 failed), --verify-dirty 90/90 identical with no pixel outside the touched boxes, screenshots up to date.

Merge Danger

Door: two-way

Blast Radius: glyph choice in cells where something moves; slightly more glyph changes there.