fix(waybar): widen the battery icon-to-text gap when discharging

The discharging `format` put a single space between the icon span and
{capacity}%, but the battery-bar glyphs carry almost no right bearing,
so the state read cramped — while charging/plugged use glyphs with their
own spacing and looked fine. Widen only the discharging line to two
spaces across all four themes that ship their own bar (boreal,
summer-night, summer-day, executive-slate).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

themes/summer-day/waybar.jsonc

@@ -58,7 +58,7 @@
     "interval": 60,
     "states": { "warning": 30, "critical": 15 },
     "max-length": 10,
-    "format": "<span size='13pt'>{icon}</span> {capacity}%",
+    "format": "<span size='13pt'>{icon}</span>  {capacity}%",
     "format-charging": "<span size='13pt'></span> {capacity}%",
     "format-plugged": "<span size='13pt'></span> {capacity}%",
     "format-full": " 100%",