Expose HttpResponse.beginWrite and update uWebSockets submodule cleanly

[Copilot]

The previous pull request suffered from massive branch pollution, mistakenly including over 7,500 generated files, built binaries, and Node.js headers. This PR replaces that history with a clean, rebased commit chain containing only the intended minimal changes against the master branch.

Submodule Updates

• uWebSockets: Cleanly bumped to fe7c01a477b688a7743f754fee33bdd78d52ad91 (includes upstream HttpResponse::beginWrite support).

Native Bindings

• HttpResponseWrapper: Exposed beginWrite binding (res_beginWrite) with assumeCorked() assertions to match chunked write-path semantics. Registered it to the prototype template across secure and non-secure protocols.

TypeScript Definitions

• docs/index.d.ts: Declared beginWrite() : HttpResponse on the HttpResponse interface.

res.writeStatus("200 OK")
   .writeHeader("Content-Type", "text/plain");

res.beginWrite(); // flush headers & start chunked transfer-encoding
res.write("chunk 1");
res.write("chunk 2");
res.end();