fix(complete): Include positionals in subcommands

Fixes #5139

clap_complete/src/dynamic/completer.rs

@@ -63,7 +63,7 @@ pub fn complete(
         if let Ok(value) = arg.to_value() {
             if let Some(next_cmd) = current_cmd.find_subcommand(value) {
                 current_cmd = next_cmd;
-                pos_index = 0;
+                pos_index = 1;
                 continue;
             }
         }

clap_complete/tests/testsuite/dynamic.rs

@@ -113,7 +113,10 @@ fn suggest_subcommand_positional() {
 
     snapbox::assert_eq(
         "--help\tPrint help (see more with '--help')
--h\tPrint help (see more with '--help')",
+-h\tPrint help (see more with '--help')
+hello-world\tSay hello to the world
+hello-moon
+goodbye-world",
         complete!(cmd, "hello-world [TAB]"),
     );
 }