chore: enter alpha prerelease mode

[felixweinberger]

Enters changesets prerelease mode with tag alpha, and adds README stubs for the two packages that didn't have one.

Motivation and Context

We want to publish @modelcontextprotocol/client and @modelcontextprotocol/server (plus the three middleware packages) as 2.0.0-alpha.N on npm under the alpha dist-tag. With .changeset/pre.json in place, the release workflow will produce -alpha.N versions and changeset publish will publish under the alpha tag automatically (not latest).

Separately, a local pnpm pack dry-run showed that packages/client/ and packages/server/ had no README.md, so their npm pages would have been blank. The three middleware packages already had READMEs that ship correctly. Added minimal stubs that point to the repo README and migration guide.

How Has This Been Tested?

Ran pnpm build:all + pnpm --filter <pkg> pack on all 5 publishable packages and inspected the tarballs:

• workspace:^ peer deps are rewritten to ^2.0.0-alpha.0 ✓
• catalog: deps are rewritten to real version ranges ✓
• No @modelcontextprotocol/core imports in the built JS (correctly bundled, 0 matches) ✓
• READMEs now present in client + server tarballs ✓

Breaking Changes

None.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context

After this merges, the next push to main will cause release.yml / changesets/action to open a "Version Packages (alpha)" PR that consumes the ~30 pending changesets and bumps all 5 packages to 2.0.0-alpha.1. Merge that PR to publish.

Follow-ups (not in this PR):

• docs/migration.md says @modelcontextprotocol/core is a published package — it's actually private: true and bundled into client/server. Stale text.
• Root README says "pre-alpha" in the banner.
• NPM_TOKEN needs verifying for publish rights on the new package names under the @modelcontextprotocol scope.

[pkg-pr-new]

Open in StackBlitz

@modelcontextprotocol/client

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/client@1823

@modelcontextprotocol/server

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/server@1823

@modelcontextprotocol/express

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/express@1823

@modelcontextprotocol/fastify

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/fastify@1823

@modelcontextprotocol/hono

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/hono@1823

@modelcontextprotocol/node

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/node@1823

commit: 8e0f935

[changeset-bot]

⚠️ No Changeset found

Latest commit: 8e0f935

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[felixweinberger]

Heads-up for whoever reviews the Version Packages PR after this lands: all 5 packages are brand new to npm, so the first publish will claim the latest dist-tag in addition to alpha (npm behavior — first publish always becomes latest). Per the changesets prerelease docs, subsequent alphas may also go to latest. We're living with it: nobody has these packages in a lockfile yet, and the README's alpha warning is what shows on the npm page. latest resolves to stable once 2.0.0 ships.