feat(tabletop): add state, setup, mounting, and stacking

Implement the tabletop library's game state store, setup seeding with
bare-type expansion, surface mount tree resolution, part placement, and
the stacking positioning process with a dependency-free SVG path helper.
Wire the public API and add unit plus vite integration tests.

packages/tabletop/tsconfig.json

@@ -7,5 +7,5 @@
     "jsx": "react-jsx"
   },
   "include": ["src"],
-  "exclude": ["src/**/*.test.ts"]
+  "exclude": ["src/__fixtures__", "src/**/*.test.ts"]
 }