fix(codex): format reset credit API errors (#3778)

tests/unit/codex-reset-credits.test.js

@@ -91,6 +91,17 @@ describe("Codex reset credits", () => {
     });
   });
 
+  it("surfaces structured upstream errors as readable messages", async () => {
+    mocks.proxyAwareFetch.mockResolvedValue({
+      ok: false,
+      status: 403,
+      json: async () => ({ error: { message: "Reset credits are unavailable for this account" } }),
+    });
+
+    const { getCodexRateLimitResetCredits } = await import("../../open-sse/services/usage/codex.js");
+    await expect(getCodexRateLimitResetCredits("token")).rejects.toThrow("Reset credits are unavailable for this account");
+  });
+
   it("GET refreshes OAuth credentials before returning reset credit details", async () => {
     const connection = {
       id: "conn_1",