tools.vcreate: rework cli arg handling to extend scaffolding and fix issues (#19889)

cmd/tools/vcreate/tests/init_with_model_arg.expect

@@ -0,0 +1,17 @@
+#!/usr/bin/env expect
+
+set timeout 3
+
+# Pass v_root as arg, since we chdir into a temp directory during testing and create a project there.
+set v_root [lindex $argv 0]
+set model [lindex $argv 1]
+
+spawn $v_root/v init $model
+
+expect "Input your project description: " { send "My Awesome V Application.\r" } timeout { exit 1 }
+expect "Input your project version: (0.0.0) " { send "0.0.1\r" } timeout { exit 1 }
+expect "Input your project license: (MIT) " { send "\r" } timeout { exit 1 }
+expect "Initialising ..." {} timeout { exit 1 }
+# The completion message is verified in `vcreate_init_test.v`.
+
+expect eof