feat(client): send a rektradar-sdk User-Agent for API attribution

The client only sent Accept (+ optional Authorization), so SDK traffic to
api.rektradar.io was indistinguishable from raw curl / browser fetch / internal
calls in server logs -- we couldn't measure real SDK adoption. Add
`User-Agent: rektradar-sdk/<version>` to every request. In browsers User-Agent
is a forbidden header and is silently dropped (no error); it takes effect in
Node/undici, where real server-side integrations live, so /v1 calls from the
SDK now show up as rektradar-sdk/* in nginx logs. SDK_VERSION is module-local
(not exported) to keep the public api-surface unchanged.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: mik3fly

src/client.test.ts

@@ -29,6 +29,16 @@ describe("RektRadar", () => {
     expect(fetchImpl.mock.calls[0]![1]?.headers?.Authorization).toBeUndefined();
   });
 
+  it("sends a rektradar-sdk User-Agent for server-log attribution", async () => {
+    const fetchImpl = vi.fn<FetchLike>().mockResolvedValue(
+      mockResponse({ address: "0xABC", score: 1, flags: [] }),
+    );
+    const rr = new RektRadar({ fetch: fetchImpl });
+    await rr.token("0xABC");
+    const ua = fetchImpl.mock.calls[0]![1]?.headers?.["User-Agent"];
+    expect(ua).toMatch(/^rektradar-sdk\/\d/);
+  });
+
   it("passes the since param to rugs()", async () => {
     const fetchImpl = vi.fn<FetchLike>().mockResolvedValue(
       mockResponse({ rugs: [], summary: null, dataDelaySeconds: 0 }),

src/client.ts

@@ -11,6 +11,13 @@ import type {
 
 export const DEFAULT_BASE_URL = "https://api.rektradar.io";
 
+// SDK version, sent as a User-Agent so API usage from the SDK is attributable
+// in server logs (vs raw curl / browser fetch). Keep in sync with package.json
+// on each release. In browsers `User-Agent` is a forbidden header and is
+// silently dropped (no error); it takes effect in Node/undici, which is where
+// real server-side integrations live.
+const SDK_VERSION = "0.1.6";
+
 /** Thrown on a non-2xx API response. */
 export class RektRadarError extends Error {
   readonly status: number;
@@ -56,7 +63,10 @@ export class RektRadar {
   }
 
   private async get<T>(path: string): Promise<T> {
-    const headers: Record<string, string> = { Accept: "application/json" };
+    const headers: Record<string, string> = {
+      Accept: "application/json",
+      "User-Agent": `rektradar-sdk/${SDK_VERSION}`,
+    };
     if (this.apiKey) {
       headers.Authorization = `Bearer ${this.apiKey}`;
     }