YAML configuration, init without a wizard, and openai-chat-completions

- /config/agent.yaml and /config/boot.yaml replace the JSON files, read
  with serde_yaml_ng (also in the agent, inside WASM).
- sausage init asks nothing and reads no SAUSAGE_* variables. It writes
  commented templates with an example for each API, and prints the path
  to edit. Until the agent is configured, agent.chat names the missing
  field. allow_no_token: true permits a local model without a key.
- The agent speaks openai-chat-completions, the format of OpenRouter,
  Ollama, and most providers. base_url follows each SDK: with /v1 for
  the OpenAI shapes, without it for Anthropic.
- Checked against the proxy with glm-5.3-flash: the agent wrote, built,
  and activated a counter plugin in 55 s.

PROTOCOL.md

@@ -19,7 +19,7 @@ Rust plugins use the SDK `sausage-plugin`. Its source is at
 | call | A JSON-RPC request. `notes.add` calls the method `add` of the plugin `notes`. |
 | interface | A set of methods. A plugin has one main interface. It can also declare endpoint interfaces. |
 | endpoint | An interface that a running process serves on a TCP port. An endpoint file tells others where it is. |
-| service | A call in `/config/boot.json`. The core starts it at boot and again after an upgrade of its plugin. |
+| service | A call in `/config/boot.yaml`. The core starts it at boot and again after an upgrade of its plugin. |
 | import | An interface of another plugin that a plugin uses. |
 | provider, consumer | The plugin that has an interface, and a plugin that imports it. |
 | journal | The central log of the world. |
@@ -36,11 +36,13 @@ Rust plugins use the SDK `sausage-plugin`. Its source is at
   state/<plugin>/             persistent state of a plugin, by convention
   state/core/journal.sqlite   the journal
   config/                     global configuration
-    boot.json                 the services
-    agent.json                API, base URL, model, and token of the agent
+    boot.yaml                 the services
+    agent.yaml                the API, base URL, model, and key of the agent
 ```
 
 - Every process can read and write all of it. There are no permissions.
+- Configuration files are YAML, with comments. Data and interface files are
+  JSON.
 - Plugin names use `a-z`, `0-9`, `-`, and `_`. The name `core` is reserved.
 - The world folder must not contain `proc`, `run`, or `self`. These names are
   mount points (section 4). The host does not start a world that has them.
@@ -287,13 +289,14 @@ for example the control interface of a web server.
 
 ## 8. Boot and services
 
-At start, the core starts each service in `/config/boot.json`, in order:
+At start, the core starts each service in `/config/boot.yaml`, in order:
 
-```json
-[
-  {"method": "secrets.serve", "params": {}},
-  {"method": "www.start", "params": {"port": 8080}}
-]
+```yaml
+- method: secrets.serve
+  params: {}
+- method: www.start
+  params:
+    port: 8080
 ```
 
 - A service is a detached call with the parent `core`. The core waits for