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/fetch/Cargo.toml

@@ -4,5 +4,7 @@ version = "0.1.0"
 edition = "2024"
 
 [dependencies]
-serde_json = "1"
+sausage-actor = { version = "0.1", path = "../../sdk", features = ["async"] }
 wstd = "0.6"
+
+[workspace]