Console pulse: one-third speed (150ms frames), 256-ramp untouched

YuKu: 'slow the flicker a bit (half or one-third speed)'. The 16-colour
blue<->grey pulse now ticks at 150ms (600ms full cycle, calm); the
256-colour terminal breathe keeps its 50ms deep ramp. Per-depth tick
variable; same in the vendored helper.

Rate proven by pty trace: 8 frames in a 1.2s transaction = 150ms
exactly. (Frame-counting via grep -c undercounts — \r overwrites
collapse frames onto one line; count matches, not lines.)

lib/ui-block.sh

@@ -41,8 +41,9 @@ _ub_paint() {
 }
 
 _ub_busy_loop() {
-  local depth pal=() i
+  local depth pal=() i tick=0.05
   depth=$(_ub_depth)
+  [[ "$depth" -eq 16 ]] && tick=0.15   # console pulse: slow, not flicker
   case "$depth" in
     256) pal=(17 19 21 27 33 39 45 39 33 27 21 19) ;;  # deep breathe: dark navy to bright blue
     16)  pal=(44 44 100 100) ;;                          # blue <-> dark grey, constant layout
@@ -57,7 +58,7 @@ _ub_busy_loop() {
       else
         printf '\r[%s] %s' "$i" "$_UB_MSG" >&"$_UB_FD"
       fi
-      sleep 0.05 || return 0
+      sleep "$tick" || return 0
     done
   done
 }