Fix: catch unknown flags in session command before API request

Previously, invalid flags like --invalid-flag were silently ignored,
causing the CLI to make API requests that returned confusing
'timestamp expired' errors. Now prints 'Unknown option' and exits.

Fixed in 21 implementations: rb, pl, php, lua, sh, cpp, d, rs, zig,
v, kt, groovy, dart, cr, raku, ps1, m, nim, hs

un.php

@@ -722,7 +722,10 @@ function main() {
                 $options['extend'] = true;
                 break;
             default:
-                if (!str_starts_with($arg, '-')) {
+                if (str_starts_with($arg, '-')) {
+                    fwrite(STDERR, RED . "Unknown option: $arg" . RESET . "\n");
+                    exit(1);
+                } else {
                     $options['source_file'] = $arg;
                 }
                 break;