fix: make systemd service portable across machines

- Add start-proxy.sh wrapper that handles nvm/fnm/volta/asdf
- Add install-service.sh for one-command installation
- Remove hardcoded node version paths from service file

docs/install-service.sh

@@ -0,0 +1,34 @@
+#!/bin/bash
+# Install antigravity-claude-proxy as a systemd user service
+# Run from anywhere - automatically detects paths
+
+set -e
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+LOCAL_BIN="$HOME/.local/bin"
+SYSTEMD_USER_DIR="$HOME/.config/systemd/user"
+
+echo "Installing antigravity-claude-proxy systemd service..."
+
+# Create directories if needed
+mkdir -p "$LOCAL_BIN"
+mkdir -p "$SYSTEMD_USER_DIR"
+
+# Copy wrapper script
+cp "$SCRIPT_DIR/start-proxy.sh" "$LOCAL_BIN/"
+chmod +x "$LOCAL_BIN/start-proxy.sh"
+echo "  Installed: $LOCAL_BIN/start-proxy.sh"
+
+# Copy service file
+cp "$SCRIPT_DIR/antigravity-claude-proxy.service" "$SYSTEMD_USER_DIR/"
+echo "  Installed: $SYSTEMD_USER_DIR/antigravity-claude-proxy.service"
+
+# Reload systemd
+systemctl --user daemon-reload
+echo "  Reloaded systemd user daemon"
+
+echo ""
+echo "Installation complete. Commands:"
+echo "  systemctl --user enable --now antigravity-claude-proxy  # Start and enable on boot"
+echo "  systemctl --user status antigravity-claude-proxy        # Check status"
+echo "  journalctl --user -u antigravity-claude-proxy -f        # View logs"