fix(forgejo-runner): only validate required vars when truly non-interactive

Check for missing token/URL only when mode is set AND there's no TTY,
so mode=default with a terminal still allows interactive prompts inside
the container.

ct/forgejo-runner.sh

@@ -63,7 +63,8 @@ function update_script() {
 }
 
 # Fail early if running unattended without required values
-if [[ -n "${mode:-}" ]]; then
+# Only check when there's no TTY (truly non-interactive, e.g. piped or scripted)
+if [[ -n "${mode:-}" && ! -t 0 ]]; then
   if [[ -z "${var_forgejo_instance:-}" ]]; then
     msg_error "var_forgejo_instance is required for unattended installs."
     exit 1