fix: register pill font size as Tailwind v4 theme token

The arbitrary text-[8px] class was not being generated by the
Tailwind v4 Vite plugin at dev time. Register --text-pill in
@theme so text-pill becomes a first-class utility that is always
generated. Uses 0.5rem (8px) with line-height 1.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/renderer/styles.css

@@ -10,6 +10,8 @@
   --color-accent: #6366f1;
   --color-accent-hover: #818cf8;
   --color-accent-muted: rgba(99, 102, 241, 0.15);
+  --text-pill: 0.5rem;
+  --text-pill--line-height: 1;
 }
 
 :root {