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/start-proxy.sh

@@ -0,0 +1,49 @@
+#!/bin/bash
+# Wrapper script for antigravity-claude-proxy that handles various Node.js version managers
+# Used by the systemd service to ensure node is available in PATH
+
+set -e
+
+# Try nvm
+if [ -z "$NVM_DIR" ]; then
+    export NVM_DIR="$HOME/.nvm"
+fi
+if [ -s "$NVM_DIR/nvm.sh" ]; then
+    source "$NVM_DIR/nvm.sh"
+fi
+
+# Try fnm
+if command -v fnm &> /dev/null; then
+    eval "$(fnm env)"
+elif [ -d "$HOME/.fnm" ]; then
+    export PATH="$HOME/.fnm:$PATH"
+    eval "$(fnm env 2>/dev/null)" || true
+fi
+
+# Try volta
+if [ -d "$HOME/.volta" ]; then
+    export VOLTA_HOME="$HOME/.volta"
+    export PATH="$VOLTA_HOME/bin:$PATH"
+fi
+
+# Try asdf
+if [ -s "$HOME/.asdf/asdf.sh" ]; then
+    source "$HOME/.asdf/asdf.sh"
+fi
+
+# Verify node is available
+if ! command -v node &> /dev/null; then
+    echo "Error: node not found in PATH after sourcing version managers" >&2
+    echo "PATH: $PATH" >&2
+    exit 1
+fi
+
+# Verify antigravity-claude-proxy is available
+if ! command -v antigravity-claude-proxy &> /dev/null; then
+    echo "Error: antigravity-claude-proxy not found in PATH" >&2
+    echo "Install with: npm install -g antigravity-claude-proxy" >&2
+    echo "PATH: $PATH" >&2
+    exit 1
+fi
+
+exec antigravity-claude-proxy "$@"