test(perf): count the long task that dispatches the J2 click

A long task's startTime precedes the click event's timestamp when the
listener runs inside it, so the start-time filter dropped the task that
performs the interaction. Long tasks now count when their range overlaps
the window: on one main thread only the dispatching task can overlap the
click. Layout shifts keep the start-time filter. J1 is unchanged (its
window starts at -Infinity).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/electron-backend-e2e/src/performance/journey-renderer-probe.spec.ts

@@ -629,7 +629,12 @@ test('drops performance entries from before the click and keeps recent-input shi
         },
     ]);
     longTask.emit([
-        { duration: 250, entryType: 'longtask', startTime: beforeClick },
+        // A buffered J1 task that ended before the click.
+        {
+            duration: 250,
+            entryType: 'longtask',
+            startTime: beforeClick - 300,
+        },
         { duration: 90, entryType: 'longtask', startTime: now() },
     ]);
     openSource(fixture);
@@ -642,6 +647,30 @@ test('drops performance entries from before the click and keeps recent-input shi
     assert.deepEqual(state.longTaskDurationsMs, [90]);
 });
 
+test('counts the long task that dispatches the click although it began before the event', async () => {
+    const fixture = createOpenSourceFixture();
+    const [, longTask] = fixture.observers as [FakeObserver, FakeObserver];
+    const now = () => fixture.window.performance.now();
+    fixture.card.addEventListener('click', () => openSource(fixture));
+    fixture.card.click();
+    const clickMs =
+        (fixture.rawState().start?.epochMs ?? 0) -
+        fixture.window.performance.timeOrigin;
+    longTask.emit([
+        // Began 20 ms before the click stamp and ran through it: the task
+        // that dispatched the click and rendered the page.
+        { duration: 120, entryType: 'longtask', startTime: clickMs - 20 },
+        // Ended before the click: earlier work, not part of the journey.
+        { duration: 60, entryType: 'longtask', startTime: clickMs - 100 },
+        { duration: 70, entryType: 'longtask', startTime: now() },
+    ]);
+    await settle();
+    const state = fixture.state();
+    assert.equal(state.final, true);
+    assert.equal(state.counters.longTasks, 2);
+    assert.deepEqual(state.longTaskDurationsMs, [120, 70]);
+});
+
 test('rejects a click start whose sentinel could not be sent', async () => {
     const fixture = createOpenSourceFixture({ bridge: false });
     fixture.card.addEventListener('click', () => openSource(fixture));

apps/electron-backend-e2e/src/performance/journey-renderer-probe.ts

@@ -199,6 +199,17 @@ export function journeyRendererProbeScript(
         const entryEpochMs = performance.timeOrigin + entry.startTime;
         return entryEpochMs >= fromEpochMs && entryEpochMs <= untilEpochMs;
     };
+    // A task overlaps the window when it ends after the start. The main
+    // thread runs one task at a time, so the only task that overlaps the
+    // click is the one that dispatches it, which began before the event's
+    // timestamp and must still count.
+    const overlapsWindow = (entry: PerformanceEntry, untilEpochMs: number) => {
+        const entryEpochMs = performance.timeOrigin + entry.startTime;
+        return (
+            entryEpochMs + entry.duration >= fromEpochMs &&
+            entryEpochMs <= untilEpochMs
+        );
+    };
 
     const acceptLayoutShift = (
         entries: readonly PerformanceEntry[],
@@ -227,7 +238,7 @@ export function journeyRendererProbeScript(
         untilEpochMs: number
     ): void => {
         for (const entry of entries) {
-            if (entry.duration <= 50 || !inWindow(entry, untilEpochMs)) {
+            if (entry.duration <= 50 || !overlapsWindow(entry, untilEpochMs)) {
                 continue;
             }
             state.counters.longTasks += 1;