Shell wrapper for terminal raw mode, demo no longer sets raw mode

Added ./demo shell script that sets raw mode via stty before running
the Lisp demo and restores it on exit (including SIGINT/SIGTERM).

demo.lisp no longer attempts to set raw mode from inside SBCL —
terminal raw mode is the shell's responsibility.  This avoids the
recurring problem of sb-ext:run-program + stty not being able to
access the controlling terminal from inside sbcl --script.

demo

@@ -0,0 +1,20 @@
+#!/bin/sh
+# cl-tty demo launcher
+# Sets raw terminal mode, runs the demo, restores terminal on exit.
+# This is needed because SBCL's --script mode + run-program combo
+# can't reliably set raw mode from inside the Lisp process.
+
+SAVED=$(stty -g 2>/dev/null)
+if [ -z "$SAVED" ]; then
+    echo "ERROR: Not running in a real terminal." >&2
+    echo "       Try: sbcl --script demo.lisp" >&2
+    exit 1
+fi
+
+cleanup() {
+    stty "$SAVED" 2>/dev/null
+}
+trap cleanup EXIT INT TERM
+
+stty raw -echo -isig -icanon min 1 time 0 2>/dev/null
+sbcl --script "$(dirname "$0")/demo.lisp"