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.lua

@@ -764,7 +764,10 @@ local function main()
             options.dump_file = arg[i]
         elseif a == "--extend" then
             options.extend = true
-        elseif not a:match("^%-") then
+        elseif a:match("^%-") then
+            io.stderr:write(RED .. "Unknown option: " .. a .. RESET .. "\n")
+            os.exit(1)
+        else
             options.source_file = a
         end