[studio][Bug][Track1] Frontend rejects successful backend responses with code 200

[btlqql]

Confirmed defect

RocketMQ Studio's backend wraps successful responses with Result.ok(...), which sets the business code to 200. The frontend Axios response interceptor accepted only business code 0, so a valid HTTP 200 response containing { "code": 200, "message": "success" } was converted into a rejected promise and displayed as an error when real API mode was used.

Delivered fix

The complete fix is implemented in btlqql:agent/studio-api-response-contract at commit cf41b7c:

• accepts the backend's documented 200 success code;
• preserves compatibility with the previously accepted 0 success code;
• passes through non-envelope responses;
• continues rejecting non-success business codes with the backend message;
• retains Bearer token injection;
• adds six automated regression tests for the shared API client contract.

Verification completed

• npm ci --ignore-scripts --no-audit --no-fund
• npm test — 6 tests passed
• npm run lint — 0 errors (3 pre-existing warnings)
• npm run build — production build succeeded

This is a Track 1 frontend reliability fix associated with the RocketMQ Studio contribution program in apache/rocketmq#10600.