fix: refactor setup scripts for system-wide Node.js (no nvm)

BREAKING: Officer now uses system Node.js via NodeSource instead of nvm.

Changes:
- Removed nvm sourcing from setup.sh
- Updated Node installation to use NodeSource repository
- All npm global packages installed system-wide with sudo
- Updated PTY sidecar setup to use /usr/bin/node (system node)
- Added Pi validation (test --list-models)
- System packages now available to all users automatically

Benefits:
- Multi-user friendly: all users get same Node version
- No per-user environment setup needed
- Simpler troubleshooting (one node version)
- Services use consistent node binary
- Prevents snap node incompatibility issues

Fixes:
- 'node not found' for secondary users
- systemd services finding correct node
- Pi installation consistency across users

New Files:
- SETUP_GUIDE.md: Comprehensive installation guide
- SETUP_ANALYSIS.md: Technical analysis of previous issues

Migration:
- Remove nvm if installed (optional)
- Run: curl -fsSL https://deb.nodesource.com/setup_22.x | sudo -E bash -
- Run: sudo apt-get install -y nodejs
- Run: bash scripts/setup.sh

scripts/setup-pty-sidecar.sh

@@ -18,14 +18,24 @@ SERVICE_FILE="/etc/systemd/system/${SERVICE_NAME}.service"
 SERVICE_USER="$(whoami)"
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 PROJECT_DIR="$(dirname "$SCRIPT_DIR")"
-NODE_BIN="$(which node)"
+
+# Use system node (not nvm) for systemd service
+NODE_BIN="/usr/bin/node"
+
+if [ ! -f "$NODE_BIN" ]; then
+  fail "System Node.js not found at $NODE_BIN"
+  fail "Install Node.js 22 via NodeSource:"
+  fail "  curl -fsSL https://deb.nodesource.com/setup_22.x | sudo -E bash -"
+  fail "  sudo apt-get install -y nodejs"
+  exit 1
+fi
 
 echo ""
 echo "── PTY Sidecar (systemd service) ──"
+echo "  Node: $NODE_BIN ($("$NODE_BIN" -v))"
 
 if systemctl is-active --quiet "$SERVICE_NAME" 2>/dev/null; then
   skip "$SERVICE_NAME service already running"
-  echo "  Use 'bun run restart:sidecar' to restart"
   exit 0
 fi