Mouse selection, copy/paste, yield_to_user fixes

- Mouse text selection with highlight rendering in panes
- OSC 52 clipboard copy on selection, middle-click paste via tmux buffer
- Bracketed paste support (Event::Paste)
- yield_to_user: no tool result appended, ends turn immediately
- yield_to_user: no parameters, just a control signal
- Drop arboard dependency, use crossterm OSC 52 + tmux for clipboard

Co-Authored-By: Proof of Concept <poc@bcachefs.org>

src/mind/mod.rs

@@ -494,6 +494,7 @@ impl Mind {
             };
 
             let mut cmds = Vec::new();
+            let mut dmn_expired = false;
 
             tokio::select! {
                 biased;
@@ -526,17 +527,15 @@ impl Mind {
                     }
 
                     cmds.push(MindCommand::Compact);
+                    /*
+                     * Broken since the AST context window conversion:
                     if !self.config.no_agents {
                         cmds.push(MindCommand::Score);
                     }
+                    */
                 }
 
-                _ = tokio::time::sleep(timeout), if !has_input => {
-                    let tick = self.shared.lock().unwrap().dmn_tick();
-                    if let Some((prompt, target)) = tick {
-                        self.start_turn(&prompt, target).await;
-                    }
-                }
+                _ = tokio::time::sleep(timeout), if !has_input => dmn_expired = true,
             }
 
             if !self.config.no_agents {
@@ -562,6 +561,14 @@ impl Mind {
             if let Some(text) = pending {
                 self.start_turn(&text, StreamTarget::Conversation).await;
             }
+            /*
+            else if dmn_expired {
+                let tick = self.shared.lock().unwrap().dmn_tick();
+                if let Some((prompt, target)) = tick {
+                    self.start_turn(&prompt, target).await;
+                }
+            }
+            */
 
             self.run_commands(cmds).await;
         }