fix(app): stabilize session timeline layout continuity (#34533)

packages/app/e2e/utils/visual-stability/scenario.ts

@@ -0,0 +1,20 @@
+import type { Page, TestInfo } from "@playwright/test"
+import type { VisualPlan } from "./invariant"
+import { startVisualProbe, stopVisualProbe } from "./probe"
+import type { VisualRegionDefinition } from "./regions"
+import { reportVisualStability } from "./reporter"
+
+export async function runVisualStabilityScenario<const Regions extends Record<string, VisualRegionDefinition>>(input: {
+  page: Page
+  testInfo: TestInfo
+  name: string
+  regions: Regions
+  plan: VisualPlan<Extract<keyof Regions, string>>
+  run: () => Promise<void>
+}) {
+  await startVisualProbe(input.page, input.regions)
+  await input.run()
+  const result = await stopVisualProbe<Extract<keyof Regions, string>>(input.page)
+  await reportVisualStability(input.testInfo, input.name, result, input.plan)
+  return result
+}