A test that waits for a deadline somebody guessed is waiting for the wrong thing, so it waits for the editor (#93)

The suite spent 88% of its step time asleep: 564 s of steps, 496 s of
them in sleep(n) - fixed spans estimated by hand and then copied from
step to step. That is why it was slow, and why it flickered.

The signal is afterFrames(count, timeout) in ui/render.ts, exposed as
__gm.afterFrames(). It wakes the loop itself, because an editor that
draws nothing would never redeem a promise of a frame, and it gives up
after a timeout instead of hanging the run. settle() in the harness
waits two drawn frames (~32 ms) instead of 150-300 ms and falls back to
sleep(150) when the hook is missing (an old build): silently not
waiting would make every later check a coin toss.

Every action goes through it now - click, doubleClick, wheel, drag,
dragAsset, press, typeText, select, mutate, undo, redo - and with that
about 550 sleep() calls behind those actions became redundant, helpers
that are nothing but a mutate in a coat included. What a frame cannot
answer got its own condition instead: waitUntil(expr), play()/stop()
waiting on __gm.state.mode rather than on 300 ms, saved() for the
autosave (the two hand-written polling loops sampled at 300 ms for
something that arrives after a second), and showTab() as a real tool -
47 places called evaluate("__gm.showTab(...)") raw, and 24 of them
waited for nothing at all and read the old panel.

564 s -> 243 s of step time, the waiting share 88% -> 76%. Three kinds
of wait were kept, and each one bit when it was taken away: loading
bytes (textures, fonts), game time that a repaint cannot stand in for
(time scale, shader and particle clocks, the live values a running
graph carries), and the inertia the scroll step measures on purpose.

Two things the new speed uncovered, both real: 25-animation read the
frame menu unfiltered and had frozen an incomplete list (the CI failure
on c990dbc), and 33-render-on-change measured idleness while the
autosave of the step before was still painting - it waits for
saveStatus to leave dirty/saving now, so it measures that nothing
happens any more instead of that it waited long enough.

tools/e2e/15-aspect.mjs

@@ -50,7 +50,6 @@ export async function aspect(t) {
 
   // 15c. Fit moves the width only, to the sheet's ratio: 100 x 64/48.
   await clickText('↔ ▾');
-  await sleep(400);
   await clickText('Fit to 64 × 48');
   await sleep(500);
   const fitted = { w: await json(spriteProp('width')), h: await json(spriteProp('height')) };
@@ -107,7 +106,6 @@ export async function aspect(t) {
 
   const before = await json(spriteProp('width'));
   await clickText('↕ ▾');
-  await sleep(400);
   await clickText('Fit to 40 × 10');
   await sleep(500);
   const framed = { w: await json(spriteProp('width')), h: await json(spriteProp('height')) };
@@ -123,13 +121,11 @@ export async function aspect(t) {
   await select({ kind: 'object', holderId: 'scene1', objectIds: ['otex'], objectId: 'otex' });
   await sleep(600);
   await mutate("__gm.state.activeScene.objects.find((o) => o.id === 'otex').overrides.height = 90");
-  await sleep(400);
   check('the object row offers the fit as well', (await sizeButton('↔')) === 'menu');
   // The crowded case: an overridden, out-of-proportion row carries ↔ ▾ next to ↑ and ↺.
   check('and shows it beside the override buttons', (await json('__gm.textOverflows()')).length === 0);
   await shot('43-aspect-beside-the-override-buttons');
   await clickText('↔ ▾');
-  await sleep(400);
   await clickText('Fit to 64 × 48');
   await sleep(500);
   const override = await json("__gm.state.activeScene.objects.find((o) => o.id === 'otex').overrides");