Fixes the core half of #19491 (Cluster A).

Problem

The sibling-subcommand guard added in #19425 rejects an unknown token after a command that has registered subcommands, on the assumption that the token is a mistyped subcommand:

Unknown command `cake bake template authors`.
Available subcommands: `bake template all`.

That assumption holds for parent commands that take no arguments (i18n, cache), but it is wrong for commands that declare their own positional arguments. There the trailing token is a legitimate argument, not a subcommand.

Bake is the concrete victim: BakePlugin registers both bake template and bake template all (and the same for controller, model, fixture). TemplateCommand accepts a name argument, so bake template Articles is a valid invocation, yet the guard refuses it because bake template all shares the prefix. Only --flag-first invocations slipped through, which is why some tests stayed green.

The original change already documented the intended exemption ("Commands without siblings, commands with declared positional arguments, and option-like tokens are unaffected") - the positional-argument part was just never implemented.

Fix

A token can only be told apart from a subcommand by the matched command's own option parser. So resolve and instantiate the command first, then skip the guard when its parser declares positional arguments:

$command = $this->getCommand($io, $commands, $name);

if (
    isset($argv[0])
    && !str_starts_with($argv[0], '-')
    && $this->hasCommandsWithPrefix($commands, $name)
    && !$this->commandHasArguments($command)
) {
    // ... reject unknown subcommand
}

commandHasArguments() reads the resolved command's option parser and returns whether it defines any positional arguments. The command is now instantiated once and reused for both the check and execution.

Typo protection for argument-less parent commands (cake i18n nonsense) is preserved.

Notes

• This is the core-side fix only. Cluster B in the issue (uninitialized typed property in Bake's *AllCommand::buildOptionParser()) is a Bake bug and is fixed separately in the bake plugin.
• New regression test: a command declaring a positional argument alongside a sibling subcommand runs with its argument instead of erroring. Existing guard tests (argument-less parent still errors; option-like token unaffected) continue to pass.