test(chat): add tests for ToolCard and useToolCardState helpers

- ensure `retainDetectedOverflow` maintains correct overflow states
- verify `resolveStateAfterBodyAvailabilityChange` handles state transitions correctly based on body content availability

Author: tyulyukov

apps/web/src/components/chat/_shared/ToolCard.test.ts

@@ -0,0 +1,17 @@
+import { describe, expect, it } from "vitest";
+
+import { retainDetectedOverflow } from "./ToolCard";
+
+describe("retainDetectedOverflow", () => {
+  it("keeps overflow visible after a later transient non-overflow measurement", () => {
+    expect(retainDetectedOverflow(true, false)).toBe(true);
+  });
+
+  it("turns on overflow after it is detected", () => {
+    expect(retainDetectedOverflow(false, true)).toBe(true);
+  });
+
+  it("keeps overflow hidden before it is detected", () => {
+    expect(retainDetectedOverflow(false, false)).toBe(false);
+  });
+});

apps/web/src/components/chat/_shared/useToolCardState.test.ts

@@ -0,0 +1,38 @@
+import { describe, expect, it } from "vitest";
+
+import { resolveStateAfterBodyAvailabilityChange } from "./useToolCardState";
+
+describe("resolveStateAfterBodyAvailabilityChange", () => {
+  it("opens a latest card preview when live body content arrives after mount", () => {
+    expect(
+      resolveStateAfterBodyAvailabilityChange({
+        currentState: "collapsed",
+        previousBodyAvailable: false,
+        bodyAvailable: true,
+        defaultState: "preview",
+      }),
+    ).toBe("preview");
+  });
+
+  it("does not reopen a card that already had body content", () => {
+    expect(
+      resolveStateAfterBodyAvailabilityChange({
+        currentState: "collapsed",
+        previousBodyAvailable: true,
+        bodyAvailable: true,
+        defaultState: "preview",
+      }),
+    ).toBe("collapsed");
+  });
+
+  it("does not open cards whose default state is collapsed", () => {
+    expect(
+      resolveStateAfterBodyAvailabilityChange({
+        currentState: "collapsed",
+        previousBodyAvailable: false,
+        bodyAvailable: true,
+        defaultState: "collapsed",
+      }),
+    ).toBe("collapsed");
+  });
+});