refactor(agents): share text block extraction helper

src/agents/content-blocks.test.ts

@@ -0,0 +1,19 @@
+import { describe, expect, it } from "vitest";
+import { collectTextContentBlocks } from "./content-blocks.js";
+
+describe("collectTextContentBlocks", () => {
+  it("collects text content blocks in order", () => {
+    const blocks = [
+      { type: "text", text: "first" },
+      { type: "image", data: "abc" },
+      { type: "text", text: "second" },
+    ];
+
+    expect(collectTextContentBlocks(blocks)).toEqual(["first", "second"]);
+  });
+
+  it("ignores invalid entries and non-arrays", () => {
+    expect(collectTextContentBlocks(null)).toEqual([]);
+    expect(collectTextContentBlocks([{ type: "text", text: 1 }, undefined, "x"])).toEqual([]);
+  });
+});