chore: import upstream snapshot with attribution

tests/unit/kiro-eventstream-split.test.ts

@@ -0,0 +1,35 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import { fileURLToPath } from "node:url";
+import { dirname, join } from "node:path";
+
+// Split-guard for the kiro executor EventStream framing extraction.
+// The pure AWS EventStream binary framing (ByteQueue, CRC32, parseEventFrame) lives in
+// kiro/eventstream.ts (self-contained, no host imports). Host imports back what it uses.
+const HERE = dirname(fileURLToPath(import.meta.url));
+const EXE = join(HERE, "../../open-sse/executors");
+const HOST = join(EXE, "kiro.ts");
+const LEAF = join(EXE, "kiro/eventstream.ts");
+
+test("leaf hosts the framing primitives and does not import the host", () => {
+  const src = readFileSync(LEAF, "utf8");
+  assert.match(src, /export class ByteQueue\b/);
+  assert.match(src, /export function crc32\b/);
+  assert.match(src, /export function parseEventFrame\b/);
+  assert.doesNotMatch(src, /from "\.\.\/kiro\.ts"/);
+});
+
+test("host imports the framing primitives back from the leaf", () => {
+  const host = readFileSync(HOST, "utf8");
+  assert.match(host, /from "\.\/kiro\/eventstream\.ts"/);
+});
+
+test("crc32 is deterministic and ByteQueue buffers bytes", async () => {
+  const { crc32, ByteQueue } = await import("../../open-sse/executors/kiro/eventstream.ts");
+  const a = crc32(new Uint8Array([1, 2, 3]));
+  const b = crc32(new Uint8Array([1, 2, 3]));
+  assert.equal(a, b);
+  const q = new ByteQueue();
+  assert.equal(typeof q, "object");
+});