Breathing: deep amplitude so the pulse survives flicker fusion

At 20fps the previous narrow ramp (shades 17-33) flicker-fused into an
apparent SOLID block on the VM. Amplitude now spans dark navy (17) to
bright blue (45) in 12 steps — every frame is visibly different, cycle
is 0.6s. Speed unchanged.

lib/common.sh

@@ -115,7 +115,10 @@ ui_quiet_run() {
 
     local -a bg=()
     case "$depth" in
-        256) bg=( "48;5;17" "48;5;19" "48;5;21" "48;5;27" "48;5;33" "48;5;27" "48;5;21" "48;5;19" ) ;;
+        # Deep-amplitude breathe: dark navy (17) to BRIGHT blue (45). Adjacent
+        # 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" ) ;;
         16)  bg=( "44" "104" "44" "104" ) ;;
     esac
     local -a ch=( "|" "/" "-" "\\" )

lib/ui-block.sh

@@ -42,7 +42,7 @@ _ub_busy_loop() {
   local depth pal=() i
   depth=$(_ub_depth)
   case "$depth" in
-    256) pal=(17 18 19 20 21 27 33 27 21 20 19 18) ;;  # blue breathe
+    256) pal=(17 19 21 27 33 39 45 39 33 27 21 19) ;;  # deep breathe: dark navy to bright blue
     16)  pal=(44 104 44 104) ;;                          # blue / bright blue
     *)   pal=("|" "/" "-" "\\") ;;                       # last-resort spinner
   esac