fix: improve install.sh TTY detection and preserve existing .env on upgrade

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: barckcode

web/public/install.sh

@@ -76,8 +76,8 @@ install() {
   # Create install directory
   if [[ -d "$INSTALL_DIR" ]]; then
     warn "Directory '$INSTALL_DIR' already exists."
-    if [[ -t 0 ]] || [[ -e /dev/tty ]]; then
-      read -rp "Overwrite configuration? [y/N]: " overwrite </dev/tty 2>/dev/null || overwrite="y"
+    if [[ -t 0 ]] || { [[ -e /dev/tty ]] && echo -n '' > /dev/tty 2>/dev/null; }; then
+      read -rp "Overwrite configuration? [y/N]: " overwrite </dev/tty
     else
       overwrite="y"
       info "No TTY available, proceeding with overwrite."
@@ -93,15 +93,19 @@ install() {
   curl -fsSL -o "$INSTALL_DIR/docker-compose.yml" "$REPO_BASE/docker-compose.yml"
   success "docker-compose.yml downloaded"
 
-  # Create .env file
-  info "Generating configuration..."
-  {
-    echo "# AgentCrew configuration — generated by install.sh"
-    echo "NATS_AUTH_TOKEN=$NATS_TOKEN"
-    echo "# API_PORT=3000"
-    echo "# FRONTEND_PORT=8080"
-  } > "$INSTALL_DIR/.env"
-  success ".env created with secure NATS token"
+  # Create .env file (preserve existing to keep NATS token)
+  if [[ -f "$INSTALL_DIR/.env" ]]; then
+    info "Existing .env found, keeping current configuration."
+  else
+    info "Generating configuration..."
+    {
+      echo "# AgentCrew configuration — generated by install.sh"
+      echo "NATS_AUTH_TOKEN=$NATS_TOKEN"
+      echo "# API_PORT=3000"
+      echo "# FRONTEND_PORT=8080"
+    } > "$INSTALL_DIR/.env"
+    success ".env created with secure NATS token"
+  fi
 
   # Start the stack
   echo ""