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/boot.yaml

@@ -0,0 +1,9 @@
+# The core starts these services in order. An empty list starts no services.
+# Each method is a plugin.method name. params contains its named arguments.
+# The core waits for each result before it starts the next service.
+# After a plugin upgrade, the core restarts that plugin's services.
+# Example (replace [] with this list):
+# - method: www.start
+#   params:
+#     port: 8080
+[]