fix(frontend): finish the token migration — raw grey classes -> theme tokens

UI_REDESIGN chunk 4 was never finished: 39 app/component files still used
raw Tailwind greys, kept readable in light mode only by the !important
override sheet. In dark mode text-gray-600 is ~2.3:1 on surface, and the
light override maps it to #94a3b8 (~2.6:1 on white) — unreadable in both.

Mechanical mapping (886 classes): gray-100/200 -> ink, 300/400 -> ink-2,
500/600/700 -> ink-muted, bg 950/900/800 -> page/surface/raised,
border 800 -> line, 700/600 -> line-strong, plus hover/divide/placeholder.
Alpha suffixes kept (tokens are color-mix, so /60 works). bg-gray-700,
text-white and marketing pages left alone. text-[9px] -> text-[10px].

Frontend unverified: no Node on the authoring box (#207).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

drb-frontend/components/ui/EmptyState.tsx

@@ -7,7 +7,7 @@ interface EmptyStateProps {
   action?: ReactNode;
 }
 
-/** Consistent "nothing here yet" panel — replaces the ad-hoc `<p className="text-gray-600">` scattered across pages. */
+/** Consistent "nothing here yet" panel — replaces the ad-hoc `<p className="text-ink-muted">` scattered across pages. */
 export function EmptyState({ icon, title, description, action }: EmptyStateProps) {
   return (
     <div className="flex flex-col items-center justify-center text-center py-12 px-6 border border-dashed border-line-strong rounded-xl">

drb-frontend/components/ui/MachineOutputNotice.tsx

@@ -78,7 +78,7 @@ export function MachineOutputNotice({ variant = "block", detail, className }: Pr
     return (
       <p
         role="note"
-        className={["text-[10px] leading-snug text-gray-500 mt-1.5 pt-1.5 border-t border-gray-200", className ?? ""]
+        className={["text-[10px] leading-snug text-ink-muted mt-1.5 pt-1.5 border-t border-gray-200", className ?? ""]
           .filter(Boolean)
           .join(" ")}
       >