Add session manager for tmux.

This will open a tmux session for each monitor.
Add helper script for tmux actions.

i3/simple-terminal.sh

@@ -0,0 +1,13 @@
+#!/bin/bash
+
+# Simple fallback terminal launcher
+# Uses alacritty directly without complex session detection
+
+ALACRITTY="/home/jens/.cargo/bin/alacritty"
+
+if [ -x "$ALACRITTY" ]; then
+    exec "$ALACRITTY"
+else
+    # Fallback to xterm
+    exec xterm
+fi