fix(github-copilot): prevent failed usage checks from holding connections (#109540)

* fix(github-copilot): release failed usage responses

* test(github-copilot): preserve usage HTTP errors

Co-authored-by: ZengWen-DT <ceng.wen@xydigit.com>

---------

Co-authored-by: Peter Steinberger <steipete@gmail.com>

extensions/github-copilot/models.test.ts

@@ -242,6 +242,22 @@ describe("fetchCopilotUsage", () => {
     expect(result.windows).toHaveLength(0);
   });
 
+  it("cancels failed response bodies", async () => {
+    let canceled = false;
+    const body = new ReadableStream({
+      cancel() {
+        canceled = true;
+        throw new Error("stream already closed");
+      },
+    });
+    const mockFetch = createProviderUsageFetch(async () => new Response(body, { status: 500 }));
+
+    const result = await fetchCopilotUsage("token", 5000, mockFetch);
+
+    expect(result.error).toBe("HTTP 500");
+    expect(canceled).toBe(true);
+  });
+
   it("parses premium/chat usage from remaining percentages", async () => {
     const mockFetch = createProviderUsageFetch(async (_url, init) => {
       const headers = (init?.headers as Record<string, string> | undefined) ?? {};

extensions/github-copilot/usage.ts

@@ -38,6 +38,7 @@ export async function fetchCopilotUsage(
   );
 
   if (!res.ok) {
+    await res.body?.cancel().catch(() => undefined);
     return buildUsageHttpErrorSnapshot({
       provider: "github-copilot",
       status: res.status,