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/subconscious.rs

@@ -68,8 +68,8 @@ impl State {
     /// How long to wait before the next DMN prompt in this state.
     pub fn interval(&self) -> Duration {
         match self {
-            State::Engaged => Duration::from_secs(5),
             State::Working => Duration::from_secs(3),
+            State::Engaged => Duration::from_secs(5),
             State::Foraging => Duration::from_secs(30),
             State::Resting { .. } => Duration::from_secs(300),
             State::Paused | State::Off => Duration::from_secs(86400), // effectively never