agent: Save files when model uses rename tool (#57228)

Release Notes:

- N/A

crates/agent/src/tools/rename_tool.rs

@@ -2,6 +2,7 @@ use std::fmt::Write;
 use std::sync::Arc;
 
 use agent_client_protocol::schema as acp;
+use collections::HashSet;
 use gpui::{App, Entity, SharedString, Task};
 use project::Project;
 use schemars::JsonSchema;
@@ -95,6 +96,12 @@ impl AgentTool for RenameTool {
                 ));
             }
 
+            let buffers = transaction.0.keys().cloned().collect::<HashSet<_>>();
+            project
+                .update(cx, |project, cx| project.save_buffers(buffers, cx))
+                .await
+                .map_err(|e| format!("Rename succeeded, but failed to save renamed files: {e}"))?;
+
             let mut output = format!(
                 "Renamed `{}` to `{}` in {} file(s):\n",
                 input.symbol.symbol_name,