fix(pi): add snap node compatibility diagnostics and documentation

- Added detailed error logging to detect snap node compatibility issues
- When Pi process exits with code 1, log helpful diagnostic info including node path
- Add hint to check for snap node and reinstall via apt/nvm
- Create SNAP_NODE_COMPATIBILITY.md with full troubleshooting guide
- Document root cause: snap node has file descriptor incompatibility with Bun.spawn stdin pipes
- Provide clear installation instructions for NodeSource and nvm alternatives

scripts/setup-desktop.sh

@@ -5,14 +5,7 @@ set -euo pipefail
 # Run as the user who will own the VNC session (not root).
 # Usage: ./scripts/setup-desktop.sh <vnc-password> [resolution]
 
-if [ $# -lt 1 ]; then
-  echo "Usage: $0 <vnc-password> [resolution]"
-  echo "  vnc-password: 8 characters max (VNC protocol limitation)"
-  echo "  resolution:   optional, default 1920x1080"
-  exit 1
-fi
-
-VNC_PASS="$1"
+VNC_PASS="${1:-$(head -c 6 /dev/urandom | base64 | tr -dc 'a-zA-Z0-9' | head -c 8)}"
 RESOLUTION="${2:-1920x1080}"
 USER_NAME="$(whoami)"
 ENV_FILE="$(cd "$(dirname "$0")/.." && pwd)/.env"