v0.5.20: revert plymouth removal — back to Fedora defaults for LUKS

v0.5.10-v0.5.19 progressively ripped plymouth out (kernel cmdline,
masks, dracut omit, package -plymouth, dracut regen) trying to get
text-mode LUKS prompt. Each layer surfaced a new dependency:

- plymouth.enable=0 didn't disable plymouth-start.service
- /dev/null mask survived but plymouth ran from initramfs anyway
- omit_dracutmodules in chroot didn't take (anaconda regen overrode)
- package removal worked but dropped LUKS prompt machinery entirely
- crypt+systemd-cryptsetup re-add via dracut regen-all also didn't

Each fix added complexity. Net: 6 commits of plymouth fighting,
boot still stuck at LUKS prompt.

Strategic revert: re-add plymouth, restore Fedora defaults. plymouth
is the standard LUKS-prompt path on Fedora — works out of box. v0.6
will swap fedora-logos + plymouth theme for veilor-themed splash.

This commit:
- Adds `plymouth` back to %packages
- Removes -plymouth/-plymouth-plugin-label/-plymouth-system-theme
- Removes plymouth.enable=0/rd.plymouth=0/logo.nologo/console=tty0
  from kernel cmdline
- Removes /etc/dracut.conf.d/99-veilor-no-plymouth.conf write
- Removes dracut --regenerate-all call
- Removes /dev/null symlink masks for plymouth-* units
- Keeps GRUB_DISTRIBUTOR=veilor-os branding
- Drops GRUB_TERMINAL_OUTPUT=console + GRUB_THEME edits

Result: Fedora stock LUKS path. plymouth shows fedora splash + LUKS
prompt → user types passphrase → boot continues.

overlay/usr/local/bin/veilor-installer

@@ -377,7 +377,7 @@ __SSHKEY_DIRECTIVE__
 
 # Full hardening cmdline (installed system, not live):
 # --location=none: anaconda auto-places bootloader (UEFI grub2-efi or BIOS).
-bootloader --append="lockdown=integrity slab_nomerge init_on_alloc=1 init_on_free=1 randomize_kstack_offset=on vsyscall=none plymouth.enable=0 rd.plymouth=0 logo.nologo console=tty0"
+bootloader --append="lockdown=integrity slab_nomerge init_on_alloc=1 init_on_free=1 randomize_kstack_offset=on vsyscall=none"
 
 # Disk: zero, LUKS2 (argon2id), btrfs subvolumes (no LVM intermediary).
 # Native btrfs-on-LUKS matches Fedora KDE Spin defaults; LVM+btrfs combo
@@ -436,9 +436,7 @@ policycoreutils-python-utils
 tuned
 chrony
 firewalld
-# plymouth: removed in v0.5.13. Splash unreliable in QEMU; LUKS prompt
-# falls back to systemd-tty-ask-password-agent on tty1 (text). Cleaner
-# boot, smaller initramfs, fewer moving parts.
+plymouth
 
 # admin essentials
 git
@@ -466,9 +464,6 @@ zram-generator
 -kde-connect
 -open-vm-tools-desktop
 -mlocate
--plymouth
--plymouth-plugin-label
--plymouth-system-theme
 
 %end
 
@@ -551,49 +546,12 @@ bash $REPO/scripts/kde-theme-apply.sh
 # on tty1 — text "Please enter passphrase for disk... :" — works in
 # QEMU sendkey AND on real hardware.
 
-# Layer 1: initramfs
-mkdir -p /etc/dracut.conf.d
-cat > /etc/dracut.conf.d/99-veilor-no-plymouth.conf << 'EOF'
-omit_dracutmodules+=" plymouth "
-# Ensure systemd-cryptsetup module + systemd-ask-password agent are
-# included so LUKS prompt appears on tty1 (text mode) when plymouth
-# is omitted. Without these, dracut loops on devexists waiting for
-# an unlock that never happens.
-add_dracutmodules+=" crypt systemd-cryptsetup "
-install_items+=" /usr/bin/systemd-tty-ask-password-agent "
-EOF
-# Regenerate initramfs for ALL installed kernels with our dracut config.
-# `--regenerate-all` walks /lib/modules itself; safer than bash glob in
-# chroot where shell may be dash + nullglob unset → glob expands literally
-# → dracut --kver "/lib/modules/*/" fails silently.
-dracut --force --regenerate-all 2>&1 | tail -5 || true
-
-# Layer 2: real-root masks
-mkdir -p /etc/systemd/system
-for unit in \
-    plymouth-start.service \
-    plymouth-quit.service \
-    plymouth-quit-wait.service \
-    plymouth-read-write.service \
-    plymouth-switch-root.service \
-    systemd-ask-password-plymouth.path \
-    systemd-ask-password-plymouth.service \
-    ; do
-    ln -sf /dev/null /etc/systemd/system/$unit
-done
-
-# GRUB branding: drop fedora menu titles + theme + graphical splash.
-# Pure text-mode "hackery" boot per veilor aesthetic. Logo/theme work
-# revisits in v0.6 via plymouth + veilor-black theme.
+# GRUB branding: replace fedora distributor with veilor-os in menu titles.
+# Theme + splash kept default (plymouth handles boot UI). v0.6 will swap
+# fedora-logos with veilor-logos for full visual rebrand.
 sed -i \
     -e 's|^GRUB_DISTRIBUTOR=.*|GRUB_DISTRIBUTOR="veilor-os"|' \
-    -e 's|^GRUB_THEME=.*|GRUB_THEME=|' \
-    -e 's|^GRUB_TERMINAL_OUTPUT=.*|GRUB_TERMINAL_OUTPUT="console"|' \
-    -e '/^GRUB_BACKGROUND=/d' \
     /etc/default/grub 2>/dev/null || true
-# Append GRUB_TERMINAL_OUTPUT if not present
-grep -q '^GRUB_TERMINAL_OUTPUT=' /etc/default/grub 2>/dev/null || \
-    echo 'GRUB_TERMINAL_OUTPUT="console"' >> /etc/default/grub
 # Regen grub.cfg with new branding (anaconda already wrote one; replace).
 grub2-mkconfig -o /boot/grub2/grub.cfg 2>/dev/null || true
 [ -f /boot/efi/EFI/fedora/grub.cfg ] && \