[bug] Bound runtime HTTP response buffering

[sizumita]

Affected component

imagod

Summary

The HTTP runtime path still uses a whole-body response contract. The runner collects the entire outgoing response body into memory and returns it as a single RuntimeHttpResponse.body, but there is no explicit maximum response size.

Steps to reproduce

1. Run an HTTP component that emits a very large response body.
2. Send a request through the runner ingress.
3. Observe runner memory growth while the response is accumulated.

Expected behavior

The runner should either stream HTTP responses or enforce a clear fail-closed response size limit.

Actual behavior

runtime_response_from_hyper collects the full body into a Bytes accumulator and returns it through a whole-body runtime contract, without an obvious response size limit.

Version

3f1c39e

Environment

other

Resource impact (optional)

response memory scales with body size because the runtime contract is whole-body and has no explicit response cap.

Additional context

Evidence:

• crates/imagod-runtime-wasmtime/src/http_supervisor.rs:175
• crates/imagod-runtime-wasmtime/src/http_supervisor.rs:241
• crates/imagod-runtime-internal/src/lib.rs:134

Suggested direction:

• Add a max_http_response_body_bytes contract and fail closed when exceeded.
• Longer term, move the runtime HTTP contract toward streaming or spool-to-disk behavior.