fix: use switch_foreground in auto-switch to avoid desync after /thread bg

switch_to() returns the old foreground ID, which is None after /thread bg.
This caused the .is_some() check to fail, skipping the ThreadSwitched
notification and permanently desyncing the client. switch_foreground()
returns bool indicating success, which is the correct check here.

Co-Authored-By: Erica Stith <rexlunae@gmail.com>

Author: devin-ai-integration[bot]

crates/rustyclaw-core/src/gateway/mod.rs

@@ -1203,7 +1203,7 @@ async fn handle_connection(
                                 if let Some(last_user) = messages.iter().rev().find(|m| m.role == "user") {
                                     if let Some(better_thread_id) = thread_mgr.find_best_match(&last_user.content) {
                                         // Found a better match — switch threads
-                                        if thread_mgr.switch_to(better_thread_id).is_some() {
+                                        if thread_mgr.switch_foreground(better_thread_id) {
                                             // Get the context summary from the new foreground thread
                                             let context_summary = thread_mgr
                                                 .foreground()