fix(param-support): handle strip rules without match/drop

Cloudflare AI rule only sets flattenContent. Treat missing match as
provider-wide and missing drop as empty list to avoid crash. Fixes #1960.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/unit/param-support.test.js

@@ -0,0 +1,31 @@
+import { describe, it, expect } from "vitest";
+
+import { stripUnsupportedParams } from "../../open-sse/translator/concerns/paramSupport.js";
+
+describe("stripUnsupportedParams", () => {
+  it("flattens Cloudflare AI OpenAI content-part arrays", () => {
+    const body = {
+      messages: [
+        {
+          role: "user",
+          content: [
+            { type: "text", text: "hello " },
+            { type: "image_url", image_url: { url: "data:image/png;base64,xx" } },
+            { type: "text", text: "world" },
+          ],
+        },
+      ],
+    };
+
+    expect(() => stripUnsupportedParams("cloudflare-ai", "@cf/meta/llama-3.1-8b-instruct", body)).not.toThrow();
+    expect(body.messages[0].content).toBe("hello world");
+  });
+
+  it("still drops unsupported GitHub model params", () => {
+    const body = { temperature: 0.7, top_p: 1 };
+
+    stripUnsupportedParams("github", "gpt-5.4", body);
+
+    expect(body).toEqual({ top_p: 1 });
+  });
+});