feat: add provenance-aware worker history

crates/agen/tests/ui/locked_register_tool.rs

@@ -1,4 +1,4 @@
-use agen::Engine;
+use agen::{Engine, History};
 use agen::llm_client::capability::{
     CacheStrategy, ModelCapability, StructuredOutput, ToolCallingSupport,
 };
@@ -22,7 +22,8 @@ fn main() {
         cap,
     );
     let engine = Engine::new(client);
-    let mut locked = engine.lock();
+    let history = History::new();
+    let mut locked = engine.lock(&history);
     let def: agen::tool::ToolDefinition = Arc::new(|| panic!("unused"));
     let _ = locked.register_tool(def);
 }

crates/agen/tests/ui/locked_register_tool.stderr

@@ -1,8 +1,8 @@
 error[E0599]: no method named `register_tool` found for struct `Engine<HttpTransport<AnthropicScheme>, Locked>` in the current scope
-  --> tests/ui/locked_register_tool.rs:27:20
+  --> tests/ui/locked_register_tool.rs:28:20
    |
-27 |     let _ = locked.register_tool(def);
+28 |     let _ = locked.register_tool(def);
    |                    ^^^^^^^^^^^^^ method not found in `Engine<HttpTransport<AnthropicScheme>, Locked>`
    |
    = note: the method was found for
-           - `Engine<C>`
+           - `Engine<C, Mutable, A>`