tmux: shell exits with 127 if command not found
tmux: use override to fix set-titles under XTerm
tmux: simplify the M-Enter binding using if-shell
tmux: use absolute sizing in half-screen layouts
tmux: use full tmux command names and \; chaining
tmux: binds to move adjacent pane to right/below
tmux: preserve long lines with -J for capture-pane