feat(desktop): add layout transition switch (#36667)

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

packages/app/src/context/settings.test.ts

@@ -0,0 +1,40 @@
+import { describe, expect, test } from "bun:test"
+import {
+  layoutTransitionState,
+  maximumSunsetTimeout,
+  newLayoutDesignsDefault,
+  nextSunsetCheckDelay,
+  resolveNewLayoutDesigns,
+} from "./settings"
+
+describe("layout transition", () => {
+  test("blank profiles default to the new layout", () => {
+    expect(newLayoutDesignsDefault).toBe(true)
+  })
+
+  test("hides the transition until a sunset is scheduled", () => {
+    expect(layoutTransitionState(false, true, false, false)).toEqual({ available: false, notice: false })
+  })
+
+  test("existing profiles can switch before sunset", () => {
+    expect(layoutTransitionState(true, true, false, false)).toEqual({ available: true, notice: false })
+  })
+
+  test("preserves explicit and default layout preferences", () => {
+    expect(resolveNewLayoutDesigns(false, false, true)).toBe(false)
+    expect(resolveNewLayoutDesigns(false, undefined, false)).toBe(false)
+    expect(resolveNewLayoutDesigns(false, undefined, true)).toBe(true)
+  })
+
+  test("sunset replaces the toggle with a dismissible notice", () => {
+    expect(layoutTransitionState(true, true, true, false)).toEqual({ available: false, notice: true })
+    expect(layoutTransitionState(true, true, true, true)).toEqual({ available: false, notice: false })
+    expect(resolveNewLayoutDesigns(true, false)).toBe(true)
+  })
+
+  test("caps checks for sunsets beyond the browser timeout limit", () => {
+    expect(nextSunsetCheckDelay(maximumSunsetTimeout + 1_000, 0)).toBe(maximumSunsetTimeout)
+    expect(nextSunsetCheckDelay(10_000, 9_000)).toBe(1_000)
+    expect(nextSunsetCheckDelay(9_000, 10_000)).toBe(0)
+  })
+})