feat(ud): Phase 2, 3 and 4

docs/implementation-docs/2026-03-26-cedarjs-project-overview.md

@@ -230,7 +230,7 @@ Routes.tsx ← 4 routes added inside <Set wrap={ScaffoldLayout} title="Posts" ..
 | storybook            | Vite Storybook.                                                                                                                                                                                                                                                                                        |
 | project-config       | Read cedar.toml. getPaths/getConfig/findUp.                                                                                                                                                                                                                                                            |
 | internal             | Re-exports project-config+babel-config. buildApi/buildApiWithVite/dev/generate. Route extraction.                                                                                                                                                                                                      |
-| api-server           | Fastify. Auto-discover Lambda functions. Mount GraphQL. Custom server.ts. Exports `requestHandlers` used by the Vite API dev server.                                                                                                                                                                   |
+| api-server           | Fastify. Auto-discover Lambda functions. Mount GraphQL. Custom server.ts. Exports `requestHandlers` used by the Vite API dev server. Opt-in srvx/WinterTC path via `cedar serve api --ud` or `cedar-ud-server` binary (`buildCedarDispatcher` + `createUDServer`).                                     |
 | web-server           | Fastify for web side. Uses fastify-web adapter.                                                                                                                                                                                                                                                        |
 | fastify-web          | Fastify plugin. Static files, SPA fallback, API proxy, prerender.                                                                                                                                                                                                                                      |
 | babel-config         | Presets/plugins for api+web. registerApiSideBabelHook.                                                                                                                                                                                                                                                 |
@@ -259,6 +259,6 @@ Routes.tsx ← 4 routes added inside <Set wrap={ScaffoldLayout} title="Posts" ..
 - Entry: `entry.client.tsx` (always). \*SSR/RSC: also `entry.server.tsx`
 - Routes in `Routes.tsx` as JSX (virtual, never rendered — Babel auto-loads pages)
 - Build: Vite (web + api); api uses `build.ssr: true` + `preserveModules: true` + Babel plugin
-- Server: API always Fastify; Web: Fastify (SPA). \*SSR/RSC: Web uses Express
+- Server: API always Fastify; opt-in srvx/WinterTC via `cedar serve api --ud` or `cedar-ud-server` binary. Web: Fastify (SPA). \*SSR/RSC: Web uses Express
 - Package mgr: Yarn 4 (+ experimental support for npm and pnpm); Framework: Yarn 4 + Nx (build orchestration).
 - Codegen: compile-time (Vite plugins) + on-demand (cedar-gen)