cluster create qemu: point to `create dev` for local boot media

Feature Request

Description

talosctl cluster create qemu only offers Image Factory presets (iso, iso-secureboot, pxe, disk-image). Booting a locally built ISO works via talosctl cluster create dev --iso-path, but nothing in talosctl cluster create qemu --help mentions this. The long description only lists the presets.

Per #13923 the split is intentional: qemu goes through the Image Factory, create dev covers local assets. That makes sense, but without a hint it is easy to look at qemu alone and conclude that local boot media are unsupported.

A one-line pointer in the qemu help text would close that gap, for example:

To boot locally built assets (ISO, UKI, kernel/initramfs), use `talosctl cluster create dev`.

Checked against talosctl v1.14.1 and cmd/talosctl/cmd/mgmt/cluster/create/cmd_qemu.go on main.