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.

cli/src/services.rs

@@ -12,8 +12,8 @@ impl Host {
     /// Starts discovery in the background, then waits for each boot service in order.
     pub(crate) async fn boot(&self) -> anyhow::Result<()> {
         self.watch_plugins()?;
-        let boot: Vec<Value> = serde_json::from_slice(
-            &tokio::fs::read(self.0.world.root.join("config/boot.json")).await?,
+        let boot: Vec<Value> = serde_yaml_ng::from_slice(
+            &tokio::fs::read(self.0.world.root.join("config/boot.yaml")).await?,
         )?;
         for service in boot {
             self.start_service(