feat(bar): group rhythm + semantic @muted dim states (item 28c)

Two polish items from the 1080p review. The right cluster gains a
wider breath (margin-left 14px) before each functional group — media
(pulseaudio/cpu/memory), toggles (powerprofile/nightlight/language),
status (battery/updates/notification); a self-hiding group head
degrades to the uniform spacing. Dim states (inactive workspaces, DND
bell, muted volume) move from alpha(@text, 0.5) tints to the
palette's @muted role — safe now that 28b floor-gates muted/base >=
2.0 in every theme; the CSS comment that warned against @muted
documented the pre-28b palettes and now states the new invariant.
Whole-swap bars untouched (authored identity).

Verified: V0; V1 (rendered CSS carries the rule + 4 @muted uses);
visual — tokyo-night 1080p re-capture shows the themed backdrop
(iteration #35's fix, navy not black), the group gap, and legible
muted workspaces.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

modules/home/waybar.nix

@@ -279,13 +279,14 @@ let
       border-radius: ${toString t.ui.rounding}px;
     }
 
-    /* Dim/secondary shades are alpha(@text) tints, NOT the palette's
-       subtext/muted roles — those mean "on-surface" in some palettes
-       (flexoki-light: subtext==base, gruvbox: muted≈base) and vanish
-       against the bar (item 27; tools/check-theme-contrast.py). */
+    /* Dim states use the palette's @muted role: since item 28b it is
+       floor-guaranteed legible on @base in every theme (muted/base >=
+       2.0, gated by tools/check-theme-contrast.py) — the palettes that
+       once made it vanish (gruvbox muted≈base, item 27) were retuned.
+       Secondary-but-not-dim stays alpha(@text, 0.85). */
     #workspaces button {
       padding: 0 8px;
-      color: alpha(@text, 0.5);
+      color: @muted;
       border-radius: ${toString t.ui.rounding}px;
     }
 
@@ -314,6 +315,13 @@ let
       padding: 0 10px;
     }
 
+    /* Group rhythm (item 28c): a wider breath before each functional
+       group of the right cluster — media/stats · toggles · status —
+       on top of the uniform module spacing. A group head can self-hide
+       (e.g. no battery on desktops); grouping then degrades to the
+       uniform spacing, never breaks. */
+    #pulseaudio, #custom-powerprofile, #battery { margin-left: 14px; }
+
     /* Caffeine engaged → warm tone (the screen is being held awake). */
     #idle_inhibitor.activated { color: @warn; }
 
@@ -336,9 +344,9 @@ let
     /* notifications waiting → accent; Do-Not-Disturb → muted bell-off */
     #custom-notification.notification { color: @accent; }
     #custom-notification.dnd-none,
-    #custom-notification.dnd-notification { color: alpha(@text, 0.5); }
+    #custom-notification.dnd-notification { color: @muted; }
 
-    #pulseaudio.muted { color: alpha(@text, 0.5); }
+    #pulseaudio.muted { color: @muted; }
     #battery.warning { color: @warn; }
     #battery.critical { color: @bad; }
     #battery.charging { color: @good; }