assistant2: Restore tool uses when loading saved threads (#25942)

This PR makes it so tool uses are restored when loading saved threads in
Assistant 2.

Release Notes:

- N/A

crates/assistant2/src/thread.rs

@@ -8,8 +8,9 @@ use futures::StreamExt as _;
 use gpui::{App, Context, EventEmitter, SharedString, Task};
 use language_model::{
     LanguageModel, LanguageModelCompletionEvent, LanguageModelRegistry, LanguageModelRequest,
-    LanguageModelRequestMessage, LanguageModelRequestTool, LanguageModelToolUseId,
-    MaxMonthlySpendReachedError, MessageContent, PaymentRequiredError, Role, StopReason,
+    LanguageModelRequestMessage, LanguageModelRequestTool, LanguageModelToolResult,
+    LanguageModelToolUseId, MaxMonthlySpendReachedError, MessageContent, PaymentRequiredError,
+    Role, StopReason,
 };
 use serde::{Deserialize, Serialize};
 use util::{post_inc, TryFutureExt as _};
@@ -88,7 +89,7 @@ impl Thread {
             completion_count: 0,
             pending_completions: Vec::new(),
             tools,
-            tool_use: ToolUseState::default(),
+            tool_use: ToolUseState::new(),
         }
     }
 
@@ -99,6 +100,7 @@ impl Thread {
         _cx: &mut Context<Self>,
     ) -> Self {
         let next_message_id = MessageId(saved.messages.len());
+        let tool_use = ToolUseState::from_saved_messages(&saved.messages);
 
         Self {
             id,
@@ -120,7 +122,7 @@ impl Thread {
             completion_count: 0,
             pending_completions: Vec::new(),
             tools,
-            tool_use: ToolUseState::default(),
+            tool_use,
         }
     }
 
@@ -189,6 +191,10 @@ impl Thread {
         self.tool_use.tool_uses_for_message(id)
     }
 
+    pub fn tool_results_for_message(&self, id: MessageId) -> Vec<&LanguageModelToolResult> {
+        self.tool_use.tool_results_for_message(id)
+    }
+
     pub fn message_has_tool_results(&self, message_id: MessageId) -> bool {
         self.tool_use.message_has_tool_results(message_id)
     }