Migrating to Zod v4, marking as peer dependency, and removing zod-to-json-schema

[jake-danton]

Migrating to Zod v4, marking as peer dependency, and removing zod-to-json-schema

Note, due to changes in zod v4, I marked the "preserves schema description" test in completable.test.ts as it.skip for now and left a comment pointing to an issue describing the change. We can still have completable call describe/meta explicitly if we want it to behave differently from the rest of zod v4 and be backwards compatible.

TODO:

• Stress test completable - the new zod v4 approach is much different. All tests pass, but want to do more end-to-end testing before calling it good.
• Update docs - waiting for initial feedback before doing so

Motivation and Context

See: #555, #906, #891, #802, and (potentially) #809

It also is a first step to potentially moving to standard-schema in the future. See #164, #283

It also removes the dependency on zod-to-json-schema which is not actively maintained.

How Has This Been Tested?

• Ran all unit tests
• Confirmed
• TODO: still need to stress test completable in real app

Breaking Changes

Requires migration to zod v4

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

[andreimarcut]

can't wait to see it merged

[dclark27]

Duplicate of #869 ?