feat: scaffold TanStack Module Federation plugin

[Nsttt]

Summary

Prepare this repository to publish @module-federation/tanstack for TanStack Start on Vite and Rsbuild/Rspack. The package now isolates each bundler adapter behind its own export and uses optional peer dependencies, so a project only installs and resolves the Module Federation plugin for its bundler.

Rslib builds conditional ESM and CommonJS outputs with matching declarations. Four runnable TanStack Start applications exercise Vite, Rsbuild, same-bundler federation, and reciprocal client-side manifest interoperability.

Changes

• add the backward-compatible root and /vite adapter using @module-federation/vite
• add /rsbuild using @module-federation/rsbuild-plugin, with browser script/JSONP compatibility and optional async-node CommonJS SSR output
• default Rsbuild React and React DOM shares to eager singletons while preserving explicit overrides and caller immutability
• replace tsdown with Rslib and publish .js/.d.ts ESM plus .cjs/.d.cts CommonJS artifacts
• model Vite, Rsbuild, and both Module Federation adapters as isolated optional peers
• name the Vite pair apps/vite-host and apps/vite-remote, alongside the new
  Rsbuild/Rspack host and remote apps
• wire each host to both remote formats through manifests, with browser-only cross-bundler loading
• verify manifests, entries, exposed CSS/types, package contents, compiler hooks, clean-consumer resolution, and live four-app HTTP startup
• document the remaining same-bundler and cross-bundler SSR work in TODO.md
• retain Changesets, preview publishing, semantic PR validation, and serialized trusted npm publishing

Testing

• pnpm install --frozen-lockfile
• pnpm format:check
• pnpm exec tsc -b --force --pretty false
• pnpm typecheck
• pnpm test (22 tests, including live Vite/Rsbuild runtime shells)
• pnpm pack:tanstack
• actionlint
• docs-list
• git diff --check
• Codex autoreview: clean final pass

Review notes

Accepted findings fixed during review: remote loader stale state, Vite hydration mismatch, and preserving ESM filenames when CommonJS forcing is disabled.

Two findings were rejected with direct build evidence: Rslib 1.0.1 accepts the --lib esm and --lib cjs selectors used here, and Rsbuild's environment-scoped Module Federation instances produce both browser and SSR manifests despite sharing the upstream plugin name.

Follow-up

Follow TODO.md for the Rsbuild SSR fixture, cross-bundler server-entry transport,
shared React identity, outage recovery, and version matrix. The current examples
and tests claim client manifest interoperability only, not cross-bundler SSR
remote rendering.

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/module-federation/tanstack/@module-federation/tanstack@1

commit: c73cf94