fix(waybar): clock tooltip uses single chrono format block

Two bare `{:%…}` specs emptied the hover tooltip (box with no text).
One strftime block with an embedded newline shows date + zone; ensure
tooltip label colors on generated + summer bars.

modules/home/waybar.nix

@@ -209,9 +209,11 @@ let
       # one click away.
       on-click = "nomarchy-calendar";
       tooltip = true;
-      # The zone line stays live under auto-timezone (the tz-watch SIGUSR2
-      # reload keeps it showing the currently *detected* zone).
-      tooltip-format = "{:%A, %d %B %Y}\n{:%Z (UTC%z)}";
+      # One chrono block only: waybar/fmt empties the tooltip when two
+      # bare `{:%…}` specs are concatenated (bar format works because it
+      # is a single block). Newline + zone live under auto-timezone
+      # (tz-watch SIGUSR2 reload).
+      tooltip-format = "{:%A, %d %B %Y\n%Z (UTC%z)}";
     };
 
     # Active keyboard layout (per focused device) — only placed in
@@ -473,6 +475,15 @@ let
     #battery.warning { color: @warn; }
     #battery.critical { color: @bad; }
     #battery.charging { color: @good; }
+
+    /* Clock (and other) hover tooltips — explicit colors so an empty
+       looking box is never just “text same as background”. */
+    tooltip {
+      background: @surface;
+      border: ${toString t.ui.borderSize}px solid alpha(@accent, 0.4);
+      border-radius: ${toString t.ui.rounding}px;
+    }
+    tooltip label { color: @text; }
   '';
 in
 {