Add tool use to the orchestrator (#4)

Add tool use without sandboxing.

Currently available tools are list dir, read file, write file and exec bash.

Reviewed-on: #4
Co-authored-by: Drew Galbraith <drew@tiramisu.one>
Co-committed-by: Drew Galbraith <drew@tiramisu.one>

src/provider/mod.rs

@@ -4,16 +4,18 @@ pub use claude::ClaudeProvider;
 
 use futures::Stream;
 
-use crate::core::types::{ConversationMessage, StreamEvent};
+use crate::core::types::{ConversationMessage, StreamEvent, ToolDefinition};
 
 /// Trait for model providers that can stream conversation responses.
 ///
 /// Implementors take a conversation history and return a stream of [`StreamEvent`]s.
 /// The trait is provider-agnostic -- no Claude-specific types appear here.
 pub trait ModelProvider: Send + Sync {
-    /// Stream a response from the model given the conversation history.
+    /// Stream a response from the model given the conversation history and
+    /// available tool definitions. Pass an empty slice if no tools are available.
     fn stream<'a>(
         &'a self,
         messages: &'a [ConversationMessage],
+        tools: &'a [ToolDefinition],
     ) -> impl Stream<Item = StreamEvent> + Send + 'a;
 }