fix(app): make session navigation stable and fast (#33569)

Co-authored-by: Brendan Allan <git@brendonovich.dev>

packages/app/e2e/performance/timeline/session-tab-flash.spec.ts

@@ -47,3 +47,21 @@ benchmark("samples cached session repaint after the click", async ({ page, repor
   report(compressCachedRepaintTrace(result))
   expect(result.samples.length).toBeGreaterThan(0)
 })
+
+benchmark("prefetches every open session tab", async ({ page, report }) => {
+  const prefetched = new Set<string>()
+  await mockStressTimeline(page, {
+    onMessages: (input) => {
+      if (!input.before && input.phase === "start") prefetched.add(input.sessionID)
+    },
+  })
+  await installStressSessionTabs(page, {
+    sessionIDs: [fixture.sourceID, fixture.targetID, fixture.childID],
+  })
+  await installTimelineSettings(page)
+  await page.goto(stressSessionHref(fixture.sourceID))
+  await expectSessionTitle(page, fixture.expected.sourceTitle)
+
+  await expect.poll(() => prefetched.has(fixture.childID)).toBe(true)
+  report({ prefetched: [...prefetched] })
+})