refactor: cron payload migration cleanup (#621)

* refactor: centralize cron payload migration

* test: stabilize block streaming mocks

* test: adjust chunker fence-close case

src/agents/pi-embedded-block-chunker.test.ts

@@ -0,0 +1,34 @@
+import { describe, expect, it } from "vitest";
+
+import { EmbeddedBlockChunker } from "./pi-embedded-block-chunker.js";
+
+describe("EmbeddedBlockChunker", () => {
+  it("breaks at paragraph boundary right after fence close", () => {
+    const chunker = new EmbeddedBlockChunker({
+      minChars: 1,
+      maxChars: 40,
+      breakPreference: "paragraph",
+    });
+
+    const text = [
+      "Intro",
+      "```js",
+      "console.log('x')",
+      "```",
+      "",
+      "After first line",
+      "After second line",
+    ].join("\n");
+
+    chunker.append(text);
+
+    const chunks: string[] = [];
+    chunker.drain({ force: false, emit: (chunk) => chunks.push(chunk) });
+
+    expect(chunks.length).toBe(1);
+    expect(chunks[0]).toContain("console.log");
+    expect(chunks[0]).toMatch(/```\n?$/);
+    expect(chunks[0]).not.toContain("After");
+    expect(chunker.bufferedText).toMatch(/^After/);
+  });
+});