feat: establish facade-first runtime boundary

config/runtime-baseline.json

@@ -0,0 +1,10 @@
+{
+  "baselineId": "bitbybit-web-cad-runtime-0.1",
+  "entrypoint": "BitBybitWebCadFacade",
+  "frontendFramework": "React 18 + Vite 6 + TypeScript 5",
+  "geometry": { "provider": "BitBybit internal adapter", "status": "planned" },
+  "viewport": { "provider": "Three.js internal adapter", "package": "three", "version": "0.185.1", "baseline": "WebGL2", "status": "adapter-skeleton" },
+  "persistence": { "database": "SQLite WASM", "filesystem": "OPFS", "writer": "single worker", "status": "planned" },
+  "targetBrowsers": "Capability matrix to be locked in P0-02",
+  "status": "contract-first-prototype"
+}