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/agent.yaml

@@ -0,0 +1,46 @@
+# The configuration of the agent. Edit it before the first chat.
+# api selects the request format. Choose one complete example below.
+api: openai-responses
+# OpenAI base URLs include /v1. Do not include /responses or /chat/completions.
+base_url: https://api.openai.com/v1
+# model is the provider's model identifier.
+model: gpt-4.1
+# token is the API key. Replace CHANGE_ME with your key.
+# An empty token requires allow_no_token: true. Then no authentication header is sent.
+token: CHANGE_ME
+allow_no_token: false
+# Optional output token cap. Anthropic defaults to 32000 if omitted.
+# max_tokens: 32000
+# Optional thinking effort: off, low, medium, high, xhigh, or max.
+# The agent retries a rejected effort with the nearest accepted level.
+# thinking: high
+# Optional OpenAI override for thinking effort.
+# reasoning_effort: high
+
+# OpenAI Responses example (base_url includes the version):
+# api: openai-responses
+# base_url: https://api.openai.com/v1
+# model: gpt-4.1
+# token: YOUR_OPENAI_KEY
+# allow_no_token: false
+
+# OpenRouter example (OpenAI Chat Completions, the format of most providers):
+# api: openai-chat-completions
+# base_url: https://openrouter.ai/api/v1
+# model: anthropic/claude-sonnet-4.5
+# token: YOUR_OPENROUTER_KEY
+# allow_no_token: false
+
+# Local Ollama example (OpenAI Chat Completions, no key):
+# api: openai-chat-completions
+# base_url: http://localhost:11434/v1
+# model: llama3.2
+# token: ""
+# allow_no_token: true
+
+# Anthropic Messages example (base_url excludes the version):
+# api: anthropic-messages
+# base_url: https://api.anthropic.com
+# model: claude-sonnet-4-5
+# token: YOUR_ANTHROPIC_KEY
+# allow_no_token: false