SDK sausage-actor; examples and agent on the SDK; agent without limits

- sausage-actor: Message, messages(), send/reply/publish, async Inbox
- agent: append-only /data/history.jsonl, no caps on history, steps, waits,
  tool output, or reads; max_tokens only when configured (Anthropic: 32000)

examples/echo/Cargo.toml

@@ -4,4 +4,6 @@ version = "0.1.0"
 edition = "2024"
 
 [dependencies]
-serde_json = "1"
+sausage-actor = { version = "0.1", path = "../../sdk" }
+
+[workspace]

examples/echo/src/main.rs

@@ -1,15 +1,7 @@
-use serde_json::{json, Value};
-use std::io::{BufRead, Write};
+use sausage_actor::{json, messages, reply};
 
 fn main() {
-    let mut out = std::io::stdout().lock();
-    for line in std::io::stdin().lock().lines() {
-        let Ok(msg) = serde_json::from_str::<Value>(&line.unwrap()) else { continue };
-        if msg["body"]["type"] == "shutdown" {
-            break;
-        }
-        let env = json!({"to": msg["from"], "reply_to": msg["id"], "body": {"type": "echo", "got": msg["body"]}});
-        writeln!(out, "{env}").unwrap();
-        out.flush().unwrap();
+    for message in messages() {
+        let _ = reply(&message, json!({"type": "echo", "got": message.body}));
     }
 }