feat(ai): surface tool invocations in chat history

load_history now groups preceding tool_call + tool_result scaffolding
under each assistant reply as `tools: [{name, arguments, result}]`.
Result bodies over 2000 chars are truncated for payload size with a
`result_truncated` flag; the full value remains in training_messages.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ai/handlers.rs

@@ -704,6 +704,17 @@ pub struct RenderedHistoryMessage {
     pub role: String,
     pub content: String,
     pub is_initial: bool,
+    #[serde(skip_serializing_if = "Vec::is_empty")]
+    pub tools: Vec<HistoryToolInvocation>,
+}
+
+#[derive(Debug, Serialize)]
+pub struct HistoryToolInvocation {
+    pub name: String,
+    pub arguments: serde_json::Value,
+    pub result: String,
+    #[serde(skip_serializing_if = "std::ops::Not::not")]
+    pub result_truncated: bool,
 }
 
 #[derive(Debug, Deserialize)]
@@ -787,6 +798,16 @@ pub async fn chat_history_handler(
                     role: m.role,
                     content: m.content,
                     is_initial: m.is_initial,
+                    tools: m
+                        .tools
+                        .into_iter()
+                        .map(|t| HistoryToolInvocation {
+                            name: t.name,
+                            arguments: t.arguments,
+                            result: t.result,
+                            result_truncated: t.result_truncated,
+                        })
+                        .collect(),
                 })
                 .collect(),
             turn_count: view.turn_count,