fix(openai): strict OpenAI wire compatibility — Open WebUI can chat again

/v1/chat/completions answered ordinary client payloads with a bare HTTP 422
(a plain-text body no OpenAI client can parse), so Open WebUI showed neither
an answer nor an error — it just hung. Parse the body leniently instead:
content as string/null/content-part array, tools: null, stream: null, a
string reasoning_effort, max_completion_tokens, messages[].name and
tool_call_id, and a missing Content-Type. Unreadable bodies now come back as
an OpenAI error envelope with 400.

Responses are strict OpenAI JSON: no "tool_calls": null, finish_reason mapped
to the spec's closed set (cortiq serve's max_tokens -> length), never an empty
id, and `model` echoes the id the client requested — the model that actually
answered stays in cortiq.selected_model and X-Cortiq-Selected-Model.

Streaming is re-normalised rather than forwarded verbatim: a leading role
delta, message-shaped chunks converted to delta, one terminal finish_reason,
always a trailing data: [DONE], and an SSE error event when the upstream dies
mid-flight. Adds X-Accel-Buffering: no so a fronting proxy cannot buffer the
stream into a hang.

GET /v1/models now lists managed [[cmf.servers]] models with their live
running/healthy state, so clients can pin a local .cmf directly.

Also strips client bookkeeping keys (chat_id, session_id, metadata, features,
...) from the upstream call and drops the leftover [to_wire] debug prints.

CHANGELOG.md

@@ -3,6 +3,48 @@
 All notable changes to this project are documented here.
 The format is based on [Keep a Changelog](https://keepachangelog.com/).
 
+## [0.2.45] - 2026-08-21
+
+### Fixed
+- **Open WebUI (and every strict OpenAI client) can finally chat with the gateway.**
+  `POST /v1/chat/completions` rejected perfectly ordinary payloads with a bare HTTP 422 —
+  a plain-text body no OpenAI client can parse, which is why the chat window just spun with
+  no answer and no error. The request parser now accepts every shape real clients send:
+  `content` as a string, `null`, or an array of content parts (text parts concatenated,
+  images skipped), `tools: null`, `stream: null`, a string `reasoning_effort`
+  (`low`/`medium`/`high`) as well as a numeric budget, `max_completion_tokens` as an alias
+  for `max_tokens`, `messages[].name` and `messages[].tool_call_id` proxied through, and a
+  missing `Content-Type`. A body that genuinely cannot be read now returns an OpenAI error
+  envelope with HTTP 400.
+- **Strict OpenAI response JSON, no optional `null`s.** Absent tool calls no longer emit
+  `"tool_calls": null` (the key is omitted entirely); `finish_reason` is mapped to the
+  spec's closed set, so `cortiq serve`'s `max_tokens` reaches clients as `length`; the
+  response always carries a non-empty `id`.
+- **`model` echoes the id the client requested** (`cortiq-auto` stays `cortiq-auto`, not the
+  upstream's `cortiq`), matching OpenAI's own behaviour. The model that actually answered
+  stays in `cortiq.selected_model` and `X-Cortiq-Selected-Model`. Applies to
+  `/v1/chat/completions`, `/v1/completions` and `/v1/messages`.
+- **Streaming is re-normalised instead of forwarded verbatim.** Every chunk is reissued as a
+  strict `chat.completion.chunk`: the stream opens with a `role` delta, `message`-shaped
+  chunks are converted to `delta`, empty deltas are dropped, and it always closes with one
+  terminal `finish_reason` and `data: [DONE]` — even when the upstream stops early or dies
+  mid-flight, in which case the failure arrives as an SSE `error` event rather than a client
+  waiting forever. SSE responses also carry `X-Accel-Buffering: no` so nginx/Traefik cannot
+  buffer the stream into a hang.
+- **Client bookkeeping keys are no longer proxied upstream.** `chat_id`, `session_id`,
+  `metadata`, `features`, `background_tasks` and friends (plus a non-string `user`) are
+  stripped before the provider call, so strict backends stop rejecting the request.
+
+### Added
+- **`GET /v1/models` lists managed local CMF models.** Every `[[cmf.servers]]` entry now
+  appears alongside `cortiq-auto` and the `[[models]]` pool, with live `running`/`healthy`
+  state in a non-standard `cortiq` field, so Open WebUI and other clients can pin a local
+  `.cmf` directly. Entries also carry `created`.
+
+### Changed
+- Dropped leftover `[to_wire]` debug prints from the OpenAI provider — they wrote to stderr
+  on every single request.
+
 ## [0.2.44] - 2026-08-08
 
 ### Added