revert: replace plain CSS class with @theme text-pill token

Remove .pill-trigger CSS class and restore the idiomatic Tailwind v4
@theme approach: --text-pill in @theme generates the text-pill utility.

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 {
@@ -26,13 +28,6 @@
   -moz-osx-font-smoothing: grayscale;
 }
 
-/* ── Inline pill trigger buttons ────────────────────────────── */
-
-.pill-trigger {
-  font-size: 0.5rem;
-  line-height: 1;
-}
-
 /* ── Light mode colour overrides ────────────────────────────── */
 
 [data-theme="light"] {