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.groovy

@@ -711,7 +711,10 @@ def parseArgs(argv) {
                 args.keyExtend = true
                 break
             default:
-                if (!argv[i].startsWith('-')) {
+                if (argv[i].startsWith('-')) {
+                    System.err.println("${RED}Unknown option: ${argv[i]}${RESET}")
+                    System.exit(1)
+                } else {
                     args.sourceFile = argv[i]
                 }
         }