TTY pulse: constant layout, blue <-> dark grey (no more block-off)

The on/off pulse shifted the whole line by one character during the
dark frames (off-frame printed one space fewer than the block frame).
Per YuKu: keep the block ALWAYS present and alternate its colour
instead — blue (44) <-> dark grey (100, bright black). Layout is
constant, pulse is colour-based, nothing moves but the block itself.

Also: disable_selinux now mkdir -p's /etc/selinux before writing a
fresh config (harness caught a die on a missing parent dir).

lib/common.sh

@@ -123,9 +123,10 @@ ui_quiet_run() {
         # shades must differ enough to survive flicker fusion — a subtle ramp
         # at 20fps reads as a solid block (VM-proven).
         256) bg=( "48;5;17" "48;5;19" "48;5;21" "48;5;27" "48;5;33" "48;5;39" "48;5;45" "48;5;39" "48;5;33" "48;5;27" "48;5;21" "48;5;19" ) ;;
-        # On/off pulse, NOT shade alternation: console blues fuse to solid.
-        # Empty element = frame without the block (block breathes in/out).
-        16)  bg=( "44" "44" "" "" ) ;;
+        # Colour pulse with CONSTANT layout: blue <-> dark grey (bright black).
+        # Never remove the block on a frame — a missing block shifted the
+        # whole line by one char on the console (VM-proven).
+        16)  bg=( "44" "44" "100" "100" ) ;;
     esac
     local -a ch=( "|" "/" "-" "\\" )
 
@@ -138,20 +139,11 @@ ui_quiet_run() {
                 | tail -n 1 || true)
         if (( depth >= 16 )); then
             local code="${bg[$(( f % ${#bg[@]} ))]}"
-            if [[ -n "$code" ]]; then
             if [[ -n "$cur" ]]; then
                 printf '\r\033[%sm \033[0m %s: %s' "$code" "$msg" "$cur" >&2
             else
                 printf '\r\033[%sm \033[0m %s' "$code" "$msg" >&2
             fi
-            else
-                # block "breathes out": just the text that frame
-                if [[ -n "$cur" ]]; then
-                    printf '\r   %s: %s' "$msg" "$cur" >&2
-                else
-                    printf '\r   %s' "$msg" >&2
-                fi
-            fi
         else
             if [[ -n "$cur" ]]; then
                 printf '\r  %s %s: %s' "${ch[$(( f % ${#ch[@]} ))]}" "$msg" "$cur" >&2
@@ -357,6 +349,9 @@ disable_selinux() {
         sudo cp "$cfg" "${cfg}.bkp.$(date +%F)"
         sudo sed -i 's/^SELINUX=.*/SELINUX=disabled/' "$cfg"
     else
+        # belt-and-suspenders: on real Fedora /etc/selinux always exists, but
+        # do not die if it somehow does not
+        sudo mkdir -p "$(dirname "$cfg")"
         printf 'SELINUX=disabled\nSELINUXTYPE=targeted\n' | sudo tee "$cfg" >/dev/null
     fi
     ok "SELINUX=disabled written to $cfg (backup saved). Reboot to apply."

lib/ui-block.sh

@@ -45,7 +45,7 @@ _ub_busy_loop() {
   depth=$(_ub_depth)
   case "$depth" in
     256) pal=(17 19 21 27 33 39 45 39 33 27 21 19) ;;  # deep breathe: dark navy to bright blue
-    16)  pal=(44 44 "" "") ;;                            # on/off pulse: console blues fuse
+    16)  pal=(44 44 100 100) ;;                          # blue <-> dark grey, constant layout
     *)   pal=("|" "/" "-" "\\") ;;                       # last-resort spinner
   esac
   while :; do
@@ -53,11 +53,7 @@ _ub_busy_loop() {
       if [[ "$depth" -eq 256 ]]; then
         _ub_paint "48;5;$i" "$_UB_MSG"       # 256-colour cube background
       elif [[ "$depth" -eq 16 ]]; then
-        if [[ -n "$i" ]]; then
-          _ub_paint "$i" "$_UB_MSG"          # plain ANSI background (blue)
-        else
-          printf '\r   %s' "$_UB_MSG" >&"$_UB_FD"   # block breathes out
-        fi
+        _ub_paint "$i" "$_UB_MSG"            # blue <-> dark grey pulse
       else
         printf '\r[%s] %s' "$i" "$_UB_MSG" >&"$_UB_FD"
       fi