v0.55.0 — Sandbox probes through an executor sidecar

[0.55.0] - 2026-10-21

The sandbox console runs its connection probe through an executor

• The admin sandbox page's Test button now runs the upstream probe for the
  E2B and Aliyun Code Interpreter providers through a deployer-provided
  executor sidecar (RAYRAG_SANDBOX_EXECUTOR_URL): the provider config and the
  upstream test snippet are POSTed to that service and the answer is reported
  with the upstream success rule and message format.
• Without an executor the endpoint says the provider runs through one instead
  of faking a pass; missing credentials are reported before any network call.
  This matches v0.27.2, where the E2B provider's own execution is still a TODO
  and the Aliyun provider depends on the proprietary agentrun-sdk, which the
  image does not bundle.
• Unit tests cover the sidecar request/response and both error paths; the
  sandbox admin endpoint test and a CDP probe (E2B and Aliyun selected in the
  console) verify the full flow.