fix: compact plan and todo tool header args (#1031)

src/tests/cli/formatArgsDisplay.test.ts

@@ -0,0 +1,39 @@
+import { describe, expect, test } from "bun:test";
+import { formatArgsDisplay } from "../../cli/helpers/formatArgsDisplay";
+
+describe("formatArgsDisplay compact plan/todo headers", () => {
+  test("shows only plan item count for update_plan", () => {
+    const args = JSON.stringify({
+      explanation: "Investigating restart regression",
+      plan: [
+        { step: "Step 1", status: "pending" },
+        { step: "Step 2", status: "pending" },
+        { step: "Step 3", status: "pending" },
+      ],
+    });
+
+    expect(formatArgsDisplay(args, "update_plan").display).toBe("3 items");
+  });
+
+  test("handles singular plan item count for UpdatePlan", () => {
+    const args = JSON.stringify({
+      explanation: "One-step fix",
+      plan: [{ step: "Step 1", status: "pending" }],
+    });
+
+    expect(formatArgsDisplay(args, "UpdatePlan").display).toBe("1 item");
+  });
+
+  test("shows only todo item count for TODO tools", () => {
+    const args = JSON.stringify({
+      todos: [
+        { content: "First", status: "pending" },
+        { content: "Second", status: "in_progress" },
+      ],
+      note: "extra metadata",
+    });
+
+    expect(formatArgsDisplay(args, "TodoWrite").display).toBe("2 items");
+    expect(formatArgsDisplay(args, "write_todos").display).toBe("2 items");
+  });
+});