[wingleeio]

A tween's tracks share its ease (one Rc<Spring>) and its timing, so every track of a tween asks its spring for the same time each frame. A ui.each reorder with animate moves a thousand rows in one tween, two tracks a row: two thousand solves a frame (each an exp and a sincos) for one number. Spring now keeps the last time it was solved at (its bits) and the answer; the same bits get the same answer back. The settling-time search still calls solve directly.

Exact by construction: new test a_spring_answers_a_time_asked_again_as_solved checks the kept answer against a fresh solve bit for bit, for repeated, interleaved, signed-zero and NaN times. zgx-script: 538 tests pass; clippy and fmt clean.

Gate-style cachegrind, all scenes (origin/main vs this):

scene	main	this
script-layout	3787.8 M	3299.2 M	−12.90%
list-state	828.1 M	826.1 M	−0.24%
every other scene			−0.02 … +0.04%
mount	323.9 M	324.2 M	+0.07% in the sweep; three repeats each: main 324.03–324.22 M, this 323.97–324.28 M
anime	3840.2 M	3841.4 M	+0.03% in the sweep; repeats overlap (main 3839.8–3841.1 M, this 3839.9–3841.6 M)

🤖 Generated with Claude Code

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[github-actions]

Instruction counts (cachegrind, exact) against aaf35528; the gate fails above +1%.

scene	base	head	change
heavy-both	1,415.7 M	1,415.7 M	-0.00%
heavy-stream	1,359.3 M	1,359.3 M	+0.00%
heavy-scroll	80.4 M	80.4 M	+0.01%
lab-stream	462.0 M	462.1 M	+0.00%
lab-scroll	70.3 M	70.3 M	+0.01%
animate	397.6 M	397.6 M	+0.00%
micro-state	59.7 M	59.7 M	+0.00%
micro-vscroll-fixed	48.8 M	48.8 M	-0.03%
micro-vscroll-variable	89.1 M	89.1 M	-0.03%
micro-state-luau	82.9 M	83.0 M	+0.01%
micro-vscroll-fixed-luau	66.3 M	66.3 M	-0.01%
micro-vscroll-variable-luau	134.7 M	134.6 M	-0.03%
mount	326.8 M	327.2 M	+0.13%
script-update	1,699.9 M	1,700.2 M	+0.01%
anime	4,792.0 M	4,791.7 M	-0.01%
script-layout	4,001.6 M	3,479.1 M	-13.06%
list-state	893.6 M	894.5 M	+0.10%
style	2,146.7 M	2,146.7 M	-0.00%
widgets	2,685.2 M	2,685.2 M	+0.00%
app-mail	318.9 M	319.0 M	+0.03%
app-chat	53.2 M	53.2 M	+0.07%
app-dashboard	189.8 M	189.8 M	+0.01%
app-dashboard-sort	126.5 M	126.5 M	+0.01%
app-sketch	48.5 M	48.5 M	+0.03%
app-code	100.0 M	100.0 M	+0.03%
app-code-search	87.6 M	87.7 M	+0.04%