fix: Show error message when exiting tmux session without detaching (#110)

Prompted by #109, this change educates the user to use `Ctrl-Q` instead
of `Ctrl-C/Ctrl-D` to detach from a session.


https://github.com/user-attachments/assets/8a3af889-db17-4621-8a19-dfb90e2a2525

Fixes #109

Author: mufeez-amjad

session/tmux/tmux.go

@@ -244,6 +244,17 @@ func (t *TmuxSession) Attach() (chan struct{}, error) {
 	go func() {
 		defer t.wg.Done()
 		_, _ = io.Copy(os.Stdout, t.ptmx)
+		// When io.Copy returns, it means the connection was closed
+		// This could be due to normal detach or Ctrl-D
+		// Check if the context is done to determine if it was a normal detach
+		select {
+		case <-t.ctx.Done():
+			// Normal detach, do nothing
+		default:
+			// If context is not done, it was likely an abnormal termination (Ctrl-D)
+			// Print warning message
+			fmt.Fprintf(os.Stderr, "\n\033[31mError: Session terminated without detaching. Use Ctrl-Q to properly detach from tmux sessions.\033[0m\n")
+		}
 	}()
 
 	go func() {