feat: OpenAI and Anthropic wire-format adapters via new api input

New optional input api: ollama|openai|anthropic (default ollama —
existing flows unchanged).

- openai: OpenAI Chat Completions format (/v1/chat/completions),
  Bearer auth — targets vLLM and compatible self-hosted servers.
- anthropic: Messages API (/v1/messages), x-api-key +
  anthropic-version headers, top-level system field, mandatory
  max_tokens (fixed 4096).
- Audit outputs unchanged: model_endpoint/model_name always set;
  model_digest stays Ollama-only (no digest API on openai/anthropic,
  field is left empty rather than fabricated).
- api_key is only ever placed in auth headers; never in outputs,
  errors, or audit events (verified against the event log).
- No streaming, no tool calls.

Bump module + capability version to 0.2.0. Wire-format unit tests
for request serialization and response parsing against fixed JSON
fixtures; live smoke green on the ollama path and on the openai
path against an OpenAI-compatible local endpoint.

Signed-off-by: flemming-it <sf@flemming.it>

MODULE.md

@@ -1,23 +1,35 @@
 # llm.chat
 
-Generic Ollama-compatible LLM chat adapter. The building-block
-module any flow uses when it needs a one-shot LLM completion —
-classify, extract-fields, rewrite, decide — instead of rolling
-its own HTTP client.
+Generic LLM chat adapter. The building-block module any flow
+uses when it needs a one-shot LLM completion — classify,
+extract-fields, rewrite, decide — instead of rolling its own
+HTTP client. Speaks three wire formats, selected by the
+optional `api` input: Ollama (default), OpenAI Chat
+Completions (OpenAI, vLLM, compatible servers), and the
+Anthropic Messages API.
 
 ## Capability
 
-- `llm.chat@0.1.0`
+- `llm.chat@0.2.0`
 
 ## Inputs
 
 | Name             | Type | Description                                                     |
 | ---------------- | ---- | --------------------------------------------------------------- |
 | `prompt`         | text | The user-facing prompt.                                         |
-| `endpoint`       | text | Ollama-shaped `/api/chat` URL (e.g. `http://localhost:11434/api/chat`). |
-| `model`          | text | Model identifier (e.g. `qwen2.5:14b`, `llama3.1:8b`).           |
-| `api_key`        | text | Optional bearer token for cloud-hosted endpoints.               |
+| `endpoint`       | text | Chat endpoint URL matching the selected `api` (see below).      |
+| `model`          | text | Model identifier (e.g. `qwen2.5:14b`, `claude-fable-5`).      |
+| `api_key`        | text | Optional API key. Never appears in outputs, logs, or events.    |
 | `system_prompt`  | text | Optional system message. Empty = use the model's default.       |
+| `api`            | text | Optional wire format: `ollama` (default), `openai`, `anthropic`. |
+
+### Wire formats (`api`)
+
+| `api`       | Endpoint shape                                | Auth header                        | Notes                                                        |
+| ----------- | --------------------------------------------- | ---------------------------------- | ------------------------------------------------------------ |
+| `ollama`    | `http://localhost:11434/api/chat`             | `Authorization: Bearer` (optional) | v0.1.0 behavior, unchanged. Model-digest probe via `/api/show`. |
+| `openai`    | `https://.../v1/chat/completions`             | `Authorization: Bearer`            | OpenAI Chat Completions format — also spoken by vLLM and most self-hosted inference servers. |
+| `anthropic` | `https://api.anthropic.com/v1/messages`       | `x-api-key` + `anthropic-version`  | Messages API: `system` is a top-level field; `max_tokens` is mandatory and defaults to 4096. |
 
 ## Outputs
 
@@ -26,7 +38,7 @@ its own HTTP client.
 | `response`       | text | The assistant's plain-text reply.                                   |
 | `model_endpoint` | text | The endpoint the response was generated against.                    |
 | `model_name`     | text | The model identifier as supplied to the LLM API.                    |
-| `model_digest`   | text | SHA-256 digest of the served Ollama model. Empty for cloud APIs.    |
+| `model_digest`   | text | SHA-256 digest of the served Ollama model. Empty for `openai`/`anthropic` — those APIs expose no digest; the field is left empty rather than fabricated. |
 
 Together the three `model_*` outputs answer the audit
 question: "which exact model produced this response?" — that
@@ -43,7 +55,7 @@ permissions:
   - "net: api.anthropic.com"
 ```
 
-Loopback (local Ollama) by default. Cloud endpoints require an
+Loopback (local Ollama / vLLM) by default. Cloud endpoints require an
 operator-policy override in `~/.chain/config.yaml#security.max_permissions`.
 
 ## Why this module instead of inline HTTP
@@ -59,23 +71,22 @@ Three reasons:
    the installed modules + its declared `net:` list. A
    home-grown HTTP module would either hide its endpoints
    or be a fresh review surface every time.
-3. **Endpoint portability.** The endpoint + model are flow
-   inputs, not compile-time constants. The same flow runs
-   against `localhost:11434` in dev and a production
-   inference cluster in prod just by swapping the input.
+3. **Endpoint portability.** The endpoint, model, and wire
+   format are flow inputs, not compile-time constants. The
+   same flow runs against `localhost:11434` in dev and a
+   production vLLM cluster in prod just by swapping inputs.
 
-## Limits in v0.1.0
+## Limits in v0.2.0
 
 - No streaming. The whole reply is buffered before the output
   step fires.
 - No tool-call / function-call surface. A flow needing tool
   use composes multiple `llm.chat` steps with prompt
   engineering, or uses MCP via the bridge.
-- Cloud-provider adapters for OpenAI and Anthropic are
-  deferred until a flow actually needs them. Today the
-  Ollama wire-format is the only target.
+- Anthropic `max_tokens` is fixed at 4096 (the API requires
+  the field; a configurable input lands when a flow needs it).
 
-## Example flow
+## Example flows
 
 ```yaml
 name: classify-incoming
@@ -96,6 +107,33 @@ outputs:
   audit_model: $classify.model_digest
 ```
 
+Against a vLLM (OpenAI-compatible) server:
+
+```yaml
+steps:
+  - id: classify
+    use: llm.chat@^0
+    with:
+      api: "openai"
+      endpoint: "http://inference.internal:8000/v1/chat/completions"
+      model: "meta-llama/Llama-3.1-8B-Instruct"
+      prompt: $inputs.text
+```
+
+Against the Anthropic Messages API:
+
+```yaml
+steps:
+  - id: classify
+    use: llm.chat@^0
+    with:
+      api: "anthropic"
+      endpoint: "https://api.anthropic.com/v1/messages"
+      model: "claude-fable-5"
+      api_key: $inputs.anthropic_key
+      prompt: $inputs.text
+```
+
 ## Build
 
 ```bash