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.

src/editor/debugHook.ts

@@ -4,7 +4,17 @@ import { resolveObjects } from '../core/model/instance';
 import { findObjectHolder } from '../core/model/Project';
 import type { FrameRect } from '../core/model/texture';
 import { effectiveScale, gameClock } from '../core/time';
-import { activeDrag, Button, currentMenu, isRendering, renderCount, requestRender, ui, Widget } from '../ui';
+import {
+  activeDrag,
+  afterFrames,
+  Button,
+  currentMenu,
+  isRendering,
+  renderCount,
+  requestRender,
+  ui,
+  Widget,
+} from '../ui';
 import { particleLibrary } from '../viewport/ParticleLibrary';
 import { shaderLibrary } from '../viewport/ShaderLibrary';
 import { soundLibrary } from '../viewport/SoundLibrary';
@@ -530,6 +540,12 @@ export function installDebugHook(app: Application, state: EditorState, editor: E
     renderStats: () => ({ drawn: renderCount(), awake: isRendering() }),
     /** Draw again, whatever happens next – what a screenshot needs before it is taken. */
     wake: () => requestRender(),
+    /**
+     * Resolves once the editor has drawn `count` more frames. The checks await this instead of
+     * sleeping a guessed number of milliseconds: a frame is the editor saying it has caught up,
+     * where a deadline is only the harness hoping it has.
+     */
+    afterFrames: (count = 2, timeoutMs = 2000) => afterFrames(count, timeoutMs),
     /** Visible nodes carrying a filter – one extra render pass each; since #77 a shader is none. */
     filterCount: () => {
       let n = 0;