feat(frontend): add resizable activity split

frontend/src/shell/useActivityPanelResize.test.ts

@@ -0,0 +1,44 @@
+import { describe, expect, test } from "vitest";
+import {
+  ACTIVITY_PANEL_DEFAULT_WIDTH,
+  ACTIVITY_PANEL_STORAGE_KEY,
+  clampActivityPanelWidth,
+  getActivityPanelBounds,
+  loadActivityPanelWidth,
+  resizeWidthFromKey,
+  saveActivityPanelWidth,
+} from "./useActivityPanelResize";
+
+describe("activity panel resize contract", () => {
+  test("computes desktop bounds while preserving 512px centrally", () => {
+    expect(getActivityPanelBounds(1200)).toEqual({ min: 288, max: 576 });
+    expect(getActivityPanelBounds(1024)).toEqual({ min: 288, max: 512 });
+    expect(getActivityPanelBounds(800)).toEqual({ min: 288, max: 288 });
+  });
+
+  test("clamps finite values and falls back for invalid values", () => {
+    const bounds = { min: 288, max: 576 };
+    expect(clampActivityPanelWidth(200, bounds)).toBe(288);
+    expect(clampActivityPanelWidth(420, bounds)).toBe(420);
+    expect(clampActivityPanelWidth(900, bounds)).toBe(576);
+    expect(clampActivityPanelWidth(Number.NaN, bounds)).toBe(ACTIVITY_PANEL_DEFAULT_WIDTH);
+  });
+
+  test("maps keyboard controls to exact clamped increments", () => {
+    const bounds = { min: 288, max: 576 };
+    expect(resizeWidthFromKey(384, "ArrowLeft", false, bounds)).toBe(368);
+    expect(resizeWidthFromKey(384, "ArrowRight", true, bounds)).toBe(432);
+    expect(resizeWidthFromKey(384, "Home", false, bounds)).toBe(288);
+    expect(resizeWidthFromKey(384, "End", false, bounds)).toBe(576);
+    expect(resizeWidthFromKey(384, "Enter", false, bounds)).toBeNull();
+  });
+
+  test("loads, persists, and rejects corrupt browser values", () => {
+    localStorage.clear();
+    expect(loadActivityPanelWidth(localStorage)).toBe(ACTIVITY_PANEL_DEFAULT_WIDTH);
+    localStorage.setItem(ACTIVITY_PANEL_STORAGE_KEY, "corrupt");
+    expect(loadActivityPanelWidth(localStorage)).toBe(ACTIVITY_PANEL_DEFAULT_WIDTH);
+    saveActivityPanelWidth(448, localStorage);
+    expect(loadActivityPanelWidth(localStorage)).toBe(448);
+  });
+});