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/package.json

@@ -3,10 +3,28 @@
   "version": "0.0.1",
   "type": "module",
   "exports": {
+    ".": "./src/index.ts",
     "./theme.css": "./src/theme.css"
   },
+  "main": "./src/index.ts",
+  "types": "./src/index.ts",
+  "scripts": {
+    "test": "vitest run",
+    "lint": "eslint .",
+    "typecheck": "tsc"
+  },
   "dependencies": {
     "@fontsource-variable/geist-mono": "catalog:",
     "@fontsource-variable/outfit": "catalog:"
+  },
+  "peerDependencies": {
+    "react": "^19.0.0",
+    "react-dom": "^19.0.0"
+  },
+  "devDependencies": {
+    "@types/react": "catalog:",
+    "@types/react-dom": "catalog:",
+    "react": "catalog:",
+    "react-dom": "catalog:"
   }
 }