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/tests/host/cli.rs

@@ -59,11 +59,12 @@ fn install_probe(world: &Path) {
 async fn init_builds_agent() {
     let temporary = tempfile::tempdir().unwrap();
     let world = temporary.path().join("world");
+    // Legacy configuration variables must not affect the templates.
     let configured = || {
         let mut command = binary();
         command
             .current_dir(temporary.path())
-            .env("SAUSAGE_API", "anthropic-messages")
+            .env("SAUSAGE_API", "not-an-api")
             .env("SAUSAGE_BASE_URL", "http://127.0.0.1:1/")
             .env("SAUSAGE_MODEL", "init-test")
             .env("SAUSAGE_API_TOKEN", "fake-token")
@@ -72,11 +73,13 @@ async fn init_builds_agent() {
     };
     let failed = configured()
         .arg("init")
+        .env("SAUSAGE_HEADLESS", "not-a-boolean")
         .env("RUSTC", "/nonexistent-sausage-rustc")
         .output()
         .await
         .unwrap();
     assert!(!failed.status.success());
+    assert!(String::from_utf8_lossy(&failed.stderr).contains("nonexistent-sausage-rustc"));
     assert!(!world.exists());
     let output = configured().output().await.unwrap();
     assert!(
@@ -88,15 +91,14 @@ async fn init_builds_agent() {
     assert!(
         String::from_utf8_lossy(&output.stdout).contains("first agent build takes a few minutes")
     );
-    let config: Value =
-        serde_json::from_slice(&std::fs::read(world.join("config/agent.json")).unwrap()).unwrap();
+    let mut config: Value =
+        serde_yaml_ng::from_slice(&std::fs::read(world.join("config/agent.yaml")).unwrap())
+            .unwrap();
+    assert_eq!(config["token"], "CHANGE_ME");
+    assert_eq!(config["api"], "openai-responses");
+    assert!(String::from_utf8_lossy(&output.stdout).contains("config/agent.yaml"));
     assert_eq!(
-        config,
-        json!({"api":"anthropic-messages","base_url":"http://127.0.0.1:1","model":"init-test","token":"fake-token"})
-    );
-    assert!(String::from_utf8_lossy(&output.stdout).contains("sausage run"));
-    assert_eq!(
-        serde_json::from_slice::<Value>(&std::fs::read(world.join("config/boot.json")).unwrap())
+        serde_yaml_ng::from_slice::<Value>(&std::fs::read(world.join("config/boot.yaml")).unwrap())
             .unwrap(),
         json!([])
     );
@@ -131,6 +133,35 @@ async fn init_builds_agent() {
             .iter()
             .any(|method| method["name"] == "chat")
     );
+    let error = host
+        .call("agent.chat", json!({"text":"hello"}))
+        .await
+        .unwrap_err();
+    assert!(
+        error["message"]
+            .as_str()
+            .unwrap()
+            .contains("/config/agent.yaml")
+    );
+    assert!(error["message"].as_str().unwrap().contains("token"));
+    let mut server = super::agent::Llm::new("anthropic-messages").await;
+    config["api"] = json!("anthropic-messages");
+    config["base_url"] = json!(server.url);
+    config["model"] = json!("scripted-test");
+    config["token"] = json!("fake-token");
+    std::fs::write(
+        world.join("config/agent.yaml"),
+        serde_yaml_ng::to_string(&config).unwrap(),
+    )
+    .unwrap();
+    let caller = host.clone();
+    let turn =
+        tokio::spawn(async move { caller.call("agent.chat", json!({"text":"hello"})).await });
+    let (_, reply) = server.next().await;
+    reply
+        .send((200, server.answer("configured agent", &[])))
+        .unwrap();
+    assert_eq!(turn.await.unwrap().unwrap(), "configured agent");
     host.stop().await;
 }
 
@@ -178,7 +209,7 @@ async fn signals_work_during_boot() {
     ] {
         let (_folder, world) = world();
         std::fs::write(
-            world.join("config/boot.json"),
+            world.join("config/boot.yaml"),
             json!([
                 {"method":"core.lock","params":{"path":"boot"}},
                 {"method":"core.lock","params":{"path":"boot"}}
@@ -251,7 +282,7 @@ async fn console_error_stops_host() {
     let (_folder, world) = world();
     install_probe(&world);
     std::fs::write(
-        world.join("config/boot.json"),
+        world.join("config/boot.yaml"),
         json!([{"method":"probe.serve","params":{}}]).to_string(),
     )
     .unwrap();