## What changed
- Rename `ReqwestHttpClient` to `RouteAwareHttpClient` to reflect that delegated HTTP uses Codex's shared route-aware transport.
- Use `codex_http_client` response and error types plus transport-neutral `http` and `url` types, removing the exec server's direct `reqwest` dependency.
## Testing
- Cover fragment stripping and Unicode hostname normalization for delegated HTTP requests.
GitOrigin-RevId: 8b0fc60a76004feb57198bfb4afb1371c9ceb1bd
## Why
Frame-count backpressure does not bound the amount of executor-controlled data
retained in streamed HTTP response queues, and a single body delta could exceed
the intended wire size.
## What changed
- Limit each decoded `http/request/bodyDelta` payload to 1 MiB, split locally
produced response chunks at that boundary, and reject oversized incoming
deltas.
- Apply a shared 16 MiB byte budget across queued HTTP response streams. Release
capacity as deltas are consumed and fail a stream when the budget is
exhausted.
## Testing
Added coverage for rejecting an oversized delta and for failing a stream after
its queued deltas exhaust the shared byte budget.
GitOrigin-RevId: be9205fef44b0ec96b84b31a8e059b1cb9cd3f3b
### Why
The RMCP layer needs a Streamable HTTP client that can talk either
directly over `reqwest` or through the executor HTTP runner without
duplicating MCP session logic higher in the stack. This PR adds that
client-side transport boundary so remote Streamable HTTP MCP can reuse
the same RMCP flow as the local path.
### What
- Add a shared `rmcp-client/src/streamable_http/` module with:
- `transport_client.rs` for the local-or-remote transport enum
- `local_client.rs` for the direct `reqwest` implementation
- `remote_client.rs` for the executor-backed implementation
- `common.rs` for the small shared Streamable HTTP helpers
- Teach `RmcpClient` to build Streamable HTTP transports in either local
or remote mode while keeping the existing OAuth ownership in RMCP.
- Translate remote POST, GET, and DELETE session operations into
executor `http/request` calls.
- Preserve RMCP session expiry handling and reconnect behavior for the
remote transport.
- Add remote transport coverage in
`rmcp-client/tests/streamable_http_remote.rs` and keep the shared test
support in `rmcp-client/tests/streamable_http_test_support.rs`.
### Verification
- `cargo check -p codex-rmcp-client`
- online CI
### Stack
1. #18581 protocol
2. #18582 runner
3. #18583 RMCP client
4. #18584 manager wiring and local/remote coverage
---------
Co-authored-by: Codex <noreply@openai.com>
Celia Chen