v0.5.24: live ISO — text-mode boot + GRUB veilor branding

User wants full chained pipeline:
GRUB veilor-os → plymouth text → branded gum installer →
install progress → reboot → installed system text-clean.

Live ISO was missing pieces from the install ks polish. v0.5.24
brings live ks into parity:

- bootloader --append: add plymouth.enable=0 (kills fedora splash,
  exposes tty1 with gum installer banner immediately)
- chroot %post: GRUB_DISTRIBUTOR="veilor-os" (menu title)
- chroot %post: GRUB_CMDLINE_LINUX_DEFAULT="" (drop rhgb quiet)
- chroot %post: plymouth-set-default-theme details (text scroll
  fallback if plymouth.enable=0 ignored)
- grub2-mkconfig regen with new branding

Result on next ISO build:
- Boot from ISO → GRUB shows "veilor-os" entry
- Pick veilor-os → text scroll (no fedora splash)
- TTY1 lands on gum installer banner + menu (no plymouth swallow)
- Install completes → reboot → installed system already has the
  same text-mode boot + LUKS prompt config from v0.5.22-23

kickstart/veilor-os.ks

@@ -51,7 +51,7 @@ user --name=admin --groups=wheel --gecos="veilor admin" --password="" --plaintex
 # Note: init_on_alloc/init_on_free removed from default live cmdline —
 # they zero every memory page at boot which 5x'd KVM live boot time.
 # Re-enable per-install via veilor-firstboot.service for production.
-bootloader --location=mbr --append="lockdown=integrity slab_nomerge randomize_kstack_offset=on vsyscall=none"
+bootloader --location=mbr --append="lockdown=integrity slab_nomerge randomize_kstack_offset=on vsyscall=none plymouth.enable=0"
 
 # ── Live ISO partitioning (flat — for live rootfs build only) ──
 # NOTE: This is the *live* image kickstart. Final installed system uses
@@ -249,6 +249,16 @@ ln -sf /usr/lib/systemd/system/sddm.service /etc/systemd/system/display-manager.
 # Real installs land on graphical.target by default (set by anaconda).
 systemctl set-default multi-user.target
 
+# Branding: GRUB menu title + plymouth `details` text theme (no graphical
+# splash). Pure text-scroll boot exposes the gum installer immediately on
+# tty1 instead of plymouth swallowing it.
+sed -i \
+    -e 's|^GRUB_DISTRIBUTOR=.*|GRUB_DISTRIBUTOR="veilor-os"|' \
+    -e 's|^GRUB_CMDLINE_LINUX_DEFAULT=.*|GRUB_CMDLINE_LINUX_DEFAULT=""|' \
+    /etc/default/grub 2>/dev/null || true
+plymouth-set-default-theme details 2>/dev/null || true
+[ -f /boot/grub2/grub.cfg ] && grub2-mkconfig -o /boot/grub2/grub.cfg 2>/dev/null || true
+
 # zram swap (no disk swap; keys never leak to platter)
 dnf install -y zram-generator || true
 cat > /etc/systemd/zram-generator.conf << 'EOF'