Fix nightly rustfmt import grouping in types.rs tests

Move `use std::collections::HashMap;` into the std import block so
`cargo fmt --check` with the nightly group_imports config passes in CI.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 43d7a02b-08ff-4e7d-a8c0-afa6dfbe94b0

Author: devm33

rust/src/types.rs

@@ -5469,6 +5469,7 @@ impl Default for ExitPlanModeData {
 
 #[cfg(test)]
 mod tests {
+    use std::collections::HashMap;
     use std::path::PathBuf;
 
     use serde_json::json;
@@ -5485,7 +5486,6 @@ mod tests {
         ensure_attachment_display_names,
     };
     use crate::generated::session_events::TypedSessionEvent;
-    use std::collections::HashMap;
 
     #[test]
     fn tool_builder_composes() {