feat(tui): polish session tab animations (#39542)

packages/tui/test/component/tab-pulse.test.ts

@@ -1,6 +1,11 @@
 import { expect, test } from "bun:test"
 import { RGBA } from "@opentui/core"
-import { blendTabPulseColor, completionPulseOpacity, unreadGlowIntensity } from "../../src/component/tab-pulse"
+import {
+  blendTabPulseColor,
+  completionPulseOpacity,
+  glowIgnitionLevel,
+  unreadGlowIntensity,
+} from "../../src/component/tab-pulse"
 import { tint } from "../../src/theme/color"
 
 test("completion pulse rises quickly and fades over the remaining duration", () => {
@@ -11,6 +16,13 @@ test("completion pulse rises quickly and fades over the remaining duration", ()
   expect(completionPulseOpacity(1)).toBe(0)
 })
 
+test("glow ignition overshoots the resting level and settles back to it", () => {
+  expect(glowIgnitionLevel(0)).toBe(0)
+  expect(glowIgnitionLevel(0.3)).toBeCloseTo(1.5)
+  expect(glowIgnitionLevel(0.6)).toBeGreaterThan(1)
+  expect(glowIgnitionLevel(1)).toBe(1)
+})
+
 test("unread glow peaks behind the tab number and fades to the normal background", () => {
   const intensities = Array.from({ length: 22 }, (_, index) => unreadGlowIntensity(index, 22))
 

packages/tui/test/context/session-tabs-model.test.ts

@@ -3,13 +3,65 @@ import {
   adaptiveSessionTabLayout,
   closeSessionTab,
   cycleSessionTab,
+  moveSessionTab,
   moveSessionTabHistory,
   openSessionTab,
   recordSessionTabHistory,
+  seedSessionTabMotion,
   sessionTabComplete,
+  sessionTabOverflowWidth,
 } from "../../src/context/session-tabs-model"
 
 describe("session tabs", () => {
+  test("moves a tab to a clamped index and returns the same tabs for no-ops", () => {
+    const tabs = ["a", "b", "c"].map((sessionID) => ({ sessionID }))
+    expect(moveSessionTab(tabs, "a", 2).map((tab) => tab.sessionID)).toEqual(["b", "c", "a"])
+    expect(moveSessionTab(tabs, "c", -5).map((tab) => tab.sessionID)).toEqual(["c", "a", "b"])
+    expect(moveSessionTab(tabs, "b", 99).map((tab) => tab.sessionID)).toEqual(["a", "c", "b"])
+    expect(moveSessionTab(tabs, "b", 1)).toBe(tabs)
+    expect(moveSessionTab(tabs, "missing", 0)).toBe(tabs)
+  })
+
+  test("open seeding keeps survivors and grows the new tab from zero", () => {
+    const seeded = seedSessionTabMotion(
+      ["a", "b"],
+      ["a", "b", "c"],
+      { widths: [35, 35], selections: [1, 0], activities: [0, 1] },
+      { widths: [24, 23, 23], selections: [1, 0, 0], activities: [0, 1, 0] },
+    )
+    expect(seeded).toEqual({ widths: [35, 35, 0], selections: [1, 0, 0], activities: [0, 1, 0] })
+  })
+
+  test("close seeding keeps survivors at their current animated widths", () => {
+    const seeded = seedSessionTabMotion(
+      ["a", "b", "c"],
+      ["a", "c"],
+      { widths: [24, 23, 23], selections: [1, 0, 0], activities: [0, 0, 1] },
+      { widths: [35, 35], selections: [1, 0], activities: [0, 1] },
+    )
+    expect(seeded).toEqual({ widths: [24, 23], selections: [1, 0], activities: [0, 1] })
+  })
+
+  test("window shifts keep retained tabs and grow revealed ones", () => {
+    const seeded = seedSessionTabMotion(
+      ["a", "b", "c"],
+      ["b", "c", "d"],
+      { widths: [22, 8, 8], selections: [1, 0, 0], activities: [0, 0, 0] },
+      { widths: [8, 8, 22], selections: [0, 0, 1], activities: [0, 0, 0] },
+    )
+    expect(seeded).toEqual({ widths: [8, 8, 0], selections: [0, 0, 1], activities: [0, 0, 0] })
+  })
+
+  test("fully replaced windows jump instead of seeding", () => {
+    const values = { widths: [22], selections: [1], activities: [0] }
+    expect(seedSessionTabMotion(["a"], ["z"], values, values)).toBeUndefined()
+  })
+
+  test("overflow markers reserve room for a gap beside their digits", () => {
+    expect(sessionTabOverflowWidth(5)).toBe(3)
+    expect(sessionTabOverflowWidth(12)).toBe(4)
+  })
+
   test("opens each session once and refreshes its title", () => {
     const tabs = openSessionTab([{ sessionID: "a", title: "Old" }], { sessionID: "a", title: "New" })
     expect(tabs).toEqual([{ sessionID: "a", title: "New" }])