test(presence): rate-based cursor-throttle bound — deflake slow CI runners

The cursor-emit tests asserted a fixed <25 emits for 30 awaited mouse
moves, assuming the sweep outpaces the 50 ms throttle. On a loaded
Ubicloud runner each Playwright->Firefox->WASM round-trip can straddle
a throttle window, so 28/30 moves emitted and the test failed (twice on
main, once from a docs-only commit).

Bound by measured sweep duration instead: one emit per 50 ms window,
+1 leading edge, +2 slack. Fast machines get a tighter bound (~9-13);
slow runners scale with actual elapsed time. A broken throttle still
fails.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Lg5jwWuhFH5dL8hEcBDuP2

tests/kicad/presence-eeschema.spec.ts

@@ -233,15 +233,20 @@ test("cursor emit: mouse motion over the canvas produces throttled world coords"
 
   const cx = box!.x + box!.width / 2;
   const cy = box!.y + box!.height / 2;
+  const sweepStart = Date.now();
   for (let i = 0; i < 30; i++) {
     await page.mouse.move(cx - 150 + i * 10, cy, { steps: 1 });
   }
+  const sweepMs = Date.now() - sweepStart;
 
   const emits = await page.evaluate(
     () => (window as unknown as PresenceWindow).__cursorEmits!,
   );
   expect(emits.length).toBeGreaterThan(0);
-  expect(emits.length).toBeLessThan(25);
+  // Throttle is 50 ms (≤20 Hz). On a slow runner the awaited moves themselves
+  // can straddle throttle windows, so bound by measured sweep duration rather
+  // than a fixed count: one emit per 50 ms window, +1 leading edge, +2 slack.
+  expect(emits.length).toBeLessThanOrEqual(Math.floor(sweepMs / 50) + 3);
 
   const active = emits.filter((e) => e.active === 1);
   expect(active.length).toBeGreaterThan(0);

tests/kicad/presence-pcbnew.spec.ts

@@ -324,16 +324,20 @@ test("cursor emit: mouse motion over the canvas produces throttled world coords"
   // Sweep the pointer across the canvas center with many small steps.
   const cx = box!.x + box!.width / 2;
   const cy = box!.y + box!.height / 2;
+  const sweepStart = Date.now();
   for (let i = 0; i < 30; i++) {
     await page.mouse.move(cx - 150 + i * 10, cy, { steps: 1 });
   }
+  const sweepMs = Date.now() - sweepStart;
 
   const emits = await page.evaluate(
     () => (window as unknown as PresenceWindow).__cursorEmits!,
   );
   expect(emits.length).toBeGreaterThan(0);
-  // Throttle: 30 moves in well under a second must not emit 30 times.
-  expect(emits.length).toBeLessThan(25);
+  // Throttle is 50 ms (≤20 Hz). On a slow runner the awaited moves themselves
+  // can straddle throttle windows, so bound by measured sweep duration rather
+  // than a fixed count: one emit per 50 ms window, +1 leading edge, +2 slack.
+  expect(emits.length).toBeLessThanOrEqual(Math.floor(sweepMs / 50) + 3);
 
   const active = emits.filter((e) => e.active === 1);
   expect(active.length).toBeGreaterThan(0);