feat(design-explorer): the gallery, including what isn't there

Milestone #251 step 3 (#2260). New /design view, reachable from a Palette icon
beside Trash and Settings — a meta-surface like /rules, so an icon rather than a
sixth primary nav link, but not hidden either, since somewhere the design system
is visible is the entire point.

Renders three things, and refuses to render a fourth:

- REAL components, imported not recreated: StatusBadge, PriorityBadge, TagPill.
- REAL tokens, read at runtime via readTokens() so the page shows the live
  cascade rather than what the stylesheet claims. Grouped, swatched where the
  value is a colour, flagged where the token is mode-aware.
- Rule 65's four button variants and rule 60's type scale, listed as SPEC and
  marked missing.

That last part is the point of the step rather than a shortfall of it. Step 3's
premise was "render the real components, not copies — a gallery of look-alikes
drifts from the app within a month and then lies." Buttons have no shared
implementation to import: .btn-primary is defined four separate times in four
<style scoped> blocks, and 30 of 54 SFCs carry their own button CSS (#2273).
Drawing a button here would have made this page the fifth copy — committing the
exact drift the surface exists to catch. Same for the type scale: the three
families load (rule 59) but rule 60's sizes and weights are not tokens, so there
is nothing to read and a rendered specimen would be invented.

So the gallery reports them as gaps. A design system nobody can point at is a
design system that isn't there, and saying so is more useful than a page that
looks complete.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UaYUaouG9jjhATyuxCKrQs

frontend/src/router/index.ts

@@ -109,6 +109,13 @@ const router = createRouter({
       name: "rules",
       component: () => import("@/views/RulesView.vue"),
     },
+    {
+      // Meta-surface, same family as /rules: it describes the app rather than
+      // holding the operator's records.
+      path: "/design",
+      name: "design",
+      component: () => import("@/views/DesignView.vue"),
+    },
     {
       path: "/tasks",
       redirect: "/",