feat(ui): shared primitives (Button, Badge, Card, Input) on the tokens

Second step of the visual-redesign (tokens -> primitives -> surfaces):
a small set of shared, token-driven primitives in @trails-cool/ui so
both apps compose from one styled vocabulary instead of hand-rolling
bg-white/text-gray-* per screen.

- @trails-cool/ui now ships React components (Button variants+sizes,
  Badge tones, Card raised/subtle, Input) plus a tiny cn() helper.
  React is a peer dep; package builds with no bundling step.
- Co-located jsdom unit tests (@testing-library/react) assert roles,
  token classes, variant switching, and behavior — run in the existing
  Unit Tests gate, cross-platform, no snapshot baseline needed.
- Tailwind @source directive in both apps' styles.css so the package's
  token utility classes get generated.
- Dev-only /dev/ui gallery route in the planner renders every primitive
  in all states — a zero-dependency stand-in for Storybook. Excluded
  from production builds (NODE_ENV guard in routes.ts).

No app surfaces are refactored yet; adopting the primitives in the
topbar/sidebar/etc. is the surface task groups.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

packages/ui/tsconfig.json

@@ -0,0 +1,10 @@
+{
+  "extends": "../../tsconfig.base.json",
+  "compilerOptions": {
+    "outDir": "dist",
+    "rootDir": "src",
+    "noEmit": true
+  },
+  "include": ["src"],
+  "exclude": ["node_modules", "build", "dist"]
+}