Add build-image.sh: raw/qcow2 disk images without libvirt/virt-install

Runs `livemedia-creator --no-virt --make-disk` directly on the host to
produce a disk image any VM manager can consume (e.g. via virtpull's
`virtpull local ... --wonder-vm NAME`), instead of deploy.sh's live
virt-install/libvirt session.

An earlier version wrapped this in `mock`, mirroring
.gitea/workflows/build-iso.yaml's ISO build. That doesn't work for
--make-disk: mock's chroot has no live systemd-udevd, so udev never
populates properties for the loop device livemedia-creator creates,
and blivet's device scan crashes. --make-iso never hits this since it
never touches block devices. Reproduced identically on Fedora 44 and
43 mock chroots, confirmed fixed by running directly on the host
instead (root required, for /dev/loop-control access).

Also fixes two real kickstart incompatibilities with the --no-virt
disk-image path (applied to a scratch copy, not the shared
ingredients): the `text` display-mode directive (needed for
virt-install's netinstall console) conflicts with livemedia-creator's
own display handling, and `part / --grow` with no explicit --size
crashes livemedia-creator's upfront disk-size calculation (works fine
under virt-install, which pre-creates the disk at a known size
instead) — now configurable via --root-size.

New --extra-ks FILE flag layers one-off local content (e.g. a bespoke
user/rootpw override) onto the scratch copy without touching tracked
ingredients, following the README's existing "bespoke dish not part
of the matrix" pattern.

Factored deploy/deploy-distro.sh's dish-picker into deploy/select-dish.sh,
shared by both scripts.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

deploy/select-dish.sh

@@ -0,0 +1,27 @@
+#!/bin/bash
+# Lists cook/dishes/*guest-agents*.cfg and prompts the user to pick one.
+# Meant to be sourced (not executed) from repo root, after `cook && make all`
+# has regenerated dishes. Sets $selected_dish to the chosen dish's basename
+# (no extension) on success, or exits non-zero.
+
+mapfile -t dish_name < <(find "cook/dishes/" -maxdepth 1 -type f \( -name "*guest-agents*" \) -printf "%f\n" | sed 's/\.[^.]*$//')
+
+if [ ${#dish_name[@]} -eq 0 ]; then
+  echo "No files found in cook/dishes/."
+  exit 1
+fi
+
+echo "Available dishes:"
+for i in "${!dish_name[@]}"; do
+  echo "$((i + 1)). ${dish_name[$i]}"
+done
+
+read -r -p "Enter the number of the dish you want to select: " choice
+
+if ! [[ "$choice" =~ ^[0-9]+$ ]] || (( choice < 1 )) || (( choice > ${#dish_name[@]} )); then
+  echo "Invalid choice. Please enter a number from 1 to ${#dish_name[@]}."
+  exit 1
+fi
+
+selected_dish="${dish_name[$((choice - 1))]}"
+echo "You selected: $selected_dish"