Revert "replace try_lock() with lock_blocking() across UI thread"

This reverts commit 4225294d16.

src/agent/mod.rs

@@ -59,7 +59,7 @@ const ACTIVITY_LINGER: std::time::Duration = std::time::Duration::from_secs(5);
 
 impl Drop for ActivityGuard {
     fn drop(&mut self) {
-        { let mut st = self.agent.state.lock_blocking();
+        if let Ok(mut st) = self.agent.state.try_lock() {
             if let Some(entry) = st.activities.iter_mut().find(|a| a.id == self.id) {
                 entry.label.push_str(" (complete)");
                 entry.expires_at = std::time::Instant::now() + ACTIVITY_LINGER;

src/agent/tools/mcp_client.rs

@@ -152,7 +152,7 @@ async fn ensure_init(agent: Option<&std::sync::Arc<super::super::Agent>>) -> Res
                 let msg = format!("MCP server {} failed: {:#}", cfg.name, e);
                 dbglog!("{}", msg);
                 if let Some(a) = agent {
-                    { let mut st = a.state.lock_blocking();
+                    if let Ok(mut st) = a.state.try_lock() {
                         st.notify(msg);
                     }
                 }