Cloudflare hosting phase #1 - Express compat layer

[fredericbarthelet]

Addresses #535

This is phase 1 of Cloudflare hosting support.

One big rework not initially planned was to get read of all readFileSync API calls that can't be used in a Cloudflare worker environment. We were relying on those to:

• read handlebars template at runtime -> switch to a pre-compilation phase
• read vite manifest for entrypoint location at runtime -> switch from json file read to js module export file

I created a separate issue to move away from native Node.js API in production build : #571

I also had to make 2 additional small changes compared to original plan:

• remove the string literal from the dev only import statements to prevent esbuild from importing those (Vite deps like lightningcss are erroring wrangler build step)
• remove the widgetsDevServer exports from the @skybridge/server barrel file (for the same reason). This is still here for retro-compatibility reason, but can be broken if need be

Run pnpm create skybridge@cloudflare and then npm run cloudflare:deploy in the generated directory to deploy on Cloudflare

Greptile Summary

This PR begins Cloudflare Workers hosting support (phase 1) by adding an Express compatibility layer. The McpServer.run() method now starts the HTTP server and then conditionally imports httpServerHandler from cloudflare:node to return a Workers-compatible fetch handler. In non-Workers environments, it returns undefined. Dynamic imports in express.ts are indirected through variables to prevent Cloudflare's bundler from statically resolving dev-only dependencies.

• server.run() return type changed from Promise<void> to Promise<{ fetch: (...args: unknown[]) => unknown } | undefined> to expose the Cloudflare Workers fetch interface
• Dev-only import() calls in express.ts use variable indirection to avoid bundler static analysis
• Starter template now uses export default await server.run() for Workers module compatibility
• widgetsDevServer removed from public exports in index.ts — this is a breaking change as documentation (docs/devtools/index.mdx) still references importing it from skybridge/server

Confidence Score: 4/5

• This PR is generally safe to merge; the Cloudflare integration is well-implemented with a graceful fallback, but contains a breaking export removal that needs documentation alignment.
• The Cloudflare Workers integration follows the documented pattern correctly and degrades gracefully in non-Workers environments. The dynamic import indirection is a proven bundler technique. Score is 4 instead of 5 due to the removal of the widgetsDevServer public export without updating the documentation that references it, which will break users following the "Custom Integration" guide.
• packages/core/src/server/index.ts — removed widgetsDevServer export still referenced in documentation

Comments Outside Diff (1)

1. packages/core/src/server/index.ts, line 10 (link)

   Breaking public export removal

   The widgetsDevServer export was removed here, but docs/devtools/index.mdx (line 81) still documents it as part of the "Custom Integration" guide:

   import { devtoolsStaticServer, widgetsDevServer } from "skybridge/server";

   Users following that documentation will get an import error after this change. The docs should be updated to remove or replace this reference — or the export should be kept if it's still intended for external use.

Prompt To Fix All With AI

This is a comment left during a code review.
Path: packages/core/src/server/index.ts
Line: 10

Comment:
**Breaking public export removal**

The `widgetsDevServer` export was removed here, but `docs/devtools/index.mdx` (line 81) still documents it as part of the "Custom Integration" guide:

```typescript
import { devtoolsStaticServer, widgetsDevServer } from "skybridge/server";
```

Users following that documentation will get an import error after this change. The docs should be updated to remove or replace this reference — or the export should be kept if it's still intended for external use.

How can I resolve this? If you propose a fix, please make it concise.

_{Last reviewed commit: 25e58e2}