Reuse conversation cache when streaming edits (#30245)

Release Notes:

- Improved latency when the agent applies edits.

crates/language_model/src/language_model.rs

@@ -246,6 +246,9 @@ pub trait LanguageModel: Send + Sync {
     /// Whether this model supports tools.
     fn supports_tools(&self) -> bool;
 
+    /// Whether this model supports choosing which tool to use.
+    fn supports_tool_choice(&self, choice: LanguageModelToolChoice) -> bool;
+
     /// Returns whether this model supports "max mode";
     fn supports_max_mode(&self) -> bool {
         if self.provider_id().0 != ZED_CLOUD_PROVIDER_ID {