Eight-task plan covering: tokio-tungstenite workspace dep, refactor
responses_passthrough streaming branch into reusable responses_sse_stream,
frame parser with unit tests, WebSocket handler + read loop, router
wiring, full end-to-end integration tests, prometheus WS metrics, and a
smoke-test runbook for Codex CLI.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Pure code motion: streaming pipeline for /v1/responses now lives in a
reusable helper returning Stream<SseEvent>. HTTP handler wraps it in
axum Sse as before. No behavior change; all existing integration tests
pass unchanged. Prepares for WebSocket ingress on /responses.

…SSE events

Addresses two regressions from refactor 21f4085:
- Provider error JSON is forwarded verbatim with provider status code
  (no re-wrapping in lunaroute's error envelope).
- Synthetic stream-error SSE events use empty event name so clients
  consuming default 'message' events keep receiving them.

WebSocket handler (future task) keeps meaningful event names via the
SseEvent struct; HTTP handler strips empty names when wrapping.

…aming path

When upstream returns a non-JSON error body (plain text, HTML),
responses_sse_stream now wraps it in the same {"error": ...}
object shape used by the non-streaming branch of responses_passthrough
instead of emitting a bare JSON string. Restores byte-compatible
error responses across both code paths.

Adds responses_ws module to lunaroute-ingress with:
- ClientEvent enum (ResponseCreate variant)
- FrameError enum (MalformedJson, MissingField, UnsupportedType)
- parse_client_frame() for response.create frames
- error_frame() helper for structured WS error payloads
- 6 unit tests (all passing)

Suppresses dead_code lints until Task 4 wires the handler.
Foundation for Task 4 WebSocket handler.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

- Always inject content-type: application/json on the upstream POST built
  from the WS upgrade headers (upgrade GET has no body, so the header is
  typically absent).
- Overwrite response.stream unconditionally so clients that send
  {"stream": false} don't break the inherently-streaming WS transport.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Adds responses_websocket.rs with three tests that spin up a real axum
TCP listener, drive it with a tokio-tungstenite client, and assert
full-pipeline behavior against a wiremock upstream:
- ws_response_create_streams_events_and_records_session: verifies 3
  SSE events are forwarded as WS text frames and session events
  (Started, RequestRecorded, Completed) are stored.
- ws_runs_two_response_creates_sequentially_on_one_connection: sends
  two response.create frames on one connection; wiremock .expect(2)
  asserts both upstream POSTs land.
- ws_sends_error_frame_for_unsupported_event_type: confirms a
  response.cancel frame is rejected with type=error /
  code=unsupported_event_type before hitting the upstream.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

…oute

- First test's mock now requires content-type: application/json and stream=true
  in the upstream POST; the client frame sends stream=false, proving the WS
  bridge overwrites it.
- Unsupported event type test now asserts zero upstream requests, proving
  malformed frames don't leak into upstream.
- New test exercises the /responses compat path (no /v1 prefix), pinning
  the dual-route wiring.

Parses event type from frame payload so ws_frames_total labels map to
real Responses API events (response.create/completed/...) rather than
WebSocket transport placeholders ("text", "message"). Extends
instrumentation to outbound error frames and inbound binary frames so
abnormal sessions show up in dashboards.

Addresses roborev findings on 932e2fd.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Record ws_frames_total on every inbound text frame, labeling parse
failures as malformed_json/unsupported_event_type/invalid_request so
bad-traffic volume is visible alongside successful response.create
events. Adds unit tests pinning event_label precedence (JSON type >
SSE event name > "message").

Addresses roborev findings on c1f54b5.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Use `codex exec` (the documented subcommand form) instead of bare
`codex "…"`, and replace the non-existent `lunaroute-server logs -f`
with running the server in the foreground at debug level so WS
lifecycle logs are actually visible.

Addresses roborev findings on c66dd76.

lunaroute-server builds its log filter from config + LUNAROUTE_LOG_LEVEL,
not RUST_LOG. Fix the command so debug-level WS lifecycle logs actually
appear.

Addresses roborev finding on 7a738c0.

- lunaroute-routing: SwitchReason is Copy, use the copy instead of .clone() in the test
- integration tests: use struct-update syntax for HttpClientConfig instead of mut + default+reassign

These predate the branch but fail CI under -D warnings. Fixing here
so the Codex WS PR can merge.

Rust 1.95's clippy::unnecessary_sort_by flags comparator closures that
reduce to a Reverse key. CI runs clippy on 1.95 so both sorts in
router.rs now fail -D warnings. Local stable is 1.94 which didn't
catch this. Semantics unchanged.