chore: import upstream snapshot with attribution

tests/unit/deepseek-web-executor-split.test.ts

@@ -0,0 +1,34 @@
+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 deepseek-web executor stream-format extraction.
+// The pure content/citation formatters live in deepseek-web/stream-format.ts
+// (module-private; host imports them into transformSSE/collectSSEContent).
+const HERE = dirname(fileURLToPath(import.meta.url));
+const EXE = join(HERE, "../../open-sse/executors");
+const HOST = join(EXE, "deepseek-web.ts");
+const LEAF = join(EXE, "deepseek-web/stream-format.ts");
+
+test("leaf hosts the formatters and does not import the host", () => {
+  const src = readFileSync(LEAF, "utf8");
+  for (const sym of ["formatStreamContent", "appendSearchCitations", "isThinkingModel"]) {
+    assert.match(src, new RegExp(`export function ${sym}\\b`));
+  }
+  assert.doesNotMatch(src, /from "\.\.\/deepseek-web\.ts"/);
+});
+
+test("host imports the formatters back from the leaf", () => {
+  const host = readFileSync(HOST, "utf8");
+  assert.match(host, /from "\.\/deepseek-web\/stream-format\.ts"/);
+});
+
+test("formatStreamContent + model classifiers behave", async () => {
+  const { isThinkingModel, isSearchModel, formatStreamContent } =
+    await import("../../open-sse/executors/deepseek-web/stream-format.ts");
+  assert.equal(typeof isThinkingModel("deepseek-reasoner"), "boolean");
+  assert.equal(typeof isSearchModel("deepseek-search"), "boolean");
+  assert.equal(typeof formatStreamContent("hi", "deepseek-chat"), "string");
+});