Fix: skip hostname prompt when piped

Only show interactive prompt when stdin is a terminal.
When piped, use SPRITEDROP_HOSTNAME env var or auto-generate.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: kylemclaren

install.sh

@@ -147,14 +147,17 @@ prompt_hostname() {
     # Skip if already authenticated
     tailscale status > /dev/null 2>&1 && return 0
 
-    echo ""
-    echo -e "  ${DIM}Enter a hostname for this device in your tailnet${NC}"
-    echo -e "  ${DIM}(e.g., sprite-myproject, sprite-api)${NC}"
-    echo ""
-    read -p "  Hostname [Enter to auto-generate]: " input_hostname
-
-    if [ -n "$input_hostname" ]; then
-        TS_HOSTNAME="$input_hostname"
+    # Only prompt if running interactively (not piped)
+    if [ -t 0 ]; then
+        echo ""
+        echo -e "  ${DIM}Enter a hostname for this device in your tailnet${NC}"
+        echo -e "  ${DIM}(e.g., sprite-myproject, sprite-api)${NC}"
+        echo ""
+        read -p "  Hostname [Enter to auto-generate]: " input_hostname
+
+        if [ -n "$input_hostname" ]; then
+            TS_HOSTNAME="$input_hostname"
+        fi
     fi
 }