docs(demo): add end-to-end demo with recorded GIF

Squashes the demo-build arc: initial GIF + scripts, refactor to drive
recording through real cli.py, theme/timing tweaks, and the switch to
prompt-driven probes.

scripts/demo-teardown.sh

@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+# Undo what demo-setup.sh did. Restores any pre-existing
+# claude-bottle.json, removes the dummy SSH identity. Idempotent.
+
+set -euo pipefail
+
+cd "$(dirname "$0")/.."
+
+rm -f claude-bottle.json
+if [ -f claude-bottle.json.demo-backup ]; then
+  mv claude-bottle.json.demo-backup claude-bottle.json
+fi
+
+rm -rf "$HOME/.cache/claude-bottle-demo"