feat(11-02): replace 1113 old CSS variable references with Paperclip design tokens

- Replace all bg-[color:var(--old)] with bg-background/bg-card/bg-muted/bg-primary etc.
- Replace all text-[color:var(--old)] with text-foreground/text-muted-foreground/text-primary etc.
- Replace all border-[color:var(--line)] with border-border
- Replace all inline var(--old) with var(--new) equivalents
- Replace all rounded-[6px]/rounded-[8px] with rounded-lg
- Replace .surface class with bg-card border border-border shadow-sm
- Replace .focus-ring class with focus-visible Tailwind utilities
- Replace .mono class with font-mono
- Replace data-theme attribute with class-based dark mode
- 99 files updated, ~1265 lines changed, zero old references remaining

src/renderer/components/EntityWorkspace.tsx

@@ -14,8 +14,8 @@ export function EntityWorkspace({
   return (
     <div className="space-y-14">
       <div>
-        {eyebrow ? <div className="text-[10px] uppercase tracking-[0.08em] text-[color:var(--muted)]">{eyebrow}</div> : null}
-        <h2 className={`${eyebrow ? "mt-2" : ""} text-[18px] font-semibold tracking-[-0.01em] text-[color:var(--text)]`}>{title}</h2>
+        {eyebrow ? <div className="text-[10px] uppercase tracking-[0.08em] text-muted-foreground">{eyebrow}</div> : null}
+        <h2 className={`${eyebrow ? "mt-2" : ""} text-[18px] font-semibold tracking-[-0.01em] text-foreground`}>{title}</h2>
       </div>
       <div className="space-y-14">{primary}{secondary}</div>
     </div>