Add Effect v4 schema and HttpApiClient plugins

[nmnmcc]

🎯 Changes

• add @kubb/plugin-effect for generating Effect v4 beta schemas from OpenAPI models
• represent OpenAPI date-time values with Effect DateTime.Utc and JSON int64 values with a number-to-bigint codec
• add @kubb/plugin-effect-httpapiclient for generating typed HttpApi, endpoint groups, clients, parameter serialization, cookies, and security layers
• add runnable examples and regression coverage for nested references, date-time annotations, JSON int64 codecs, default responses, and security middleware

The two plugins are kept separate so schema generation can be used independently while the HttpApiClient plugin composes the generated Effect schemas into an Effect HTTP API client.

Related documentation Draft PR: kubb-labs/docs#145

✅ Checklist

• I have followed the steps in the Contributing guide.
• I have tested this code locally with pnpm run test.

Additional verification:

• pnpm --filter @kubb/plugin-effect test
• pnpm --filter @kubb/plugin-effect typecheck
• pnpm --filter @kubb/plugin-effect build
• pnpm --filter @kubb/plugin-effect-httpapiclient test
• pnpm --filter @kubb/plugin-effect-httpapiclient typecheck
• pnpm --filter @kubb/plugin-effect-httpapiclient build
• pnpm format
• pnpm lint:fix

🚀 Release Impact

• This change affects published code, and I have generated a changeset.
• This change is for the docs (no release).

This PR is intentionally a draft pending maintainer review.

[codesandbox]

Review or Edit in CodeSandbox

Open the branch in Web Editor • VS Code • Insiders

Open Preview

[codesandbox]

Review or Edit in CodeSandbox

Open the branch in Web Editor • VS Code • Insiders

Open Preview

[changeset-bot]

🦋 Changeset detected

Latest commit: 7463a12

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@kubb/plugin-effect-httpapiclient	Minor
@kubb/plugin-effect	Minor

Not sure what this means? Click here to learn what changesets are.

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

[stijnvanhulle]

@nmnmcc Thanks for having a look at adding Effect support in Kubb. We are preparing for Kubb v5 which means I will postpone this after the v5 release (planned in a couple of weeks). Could you also create a Github issue in why you think this would be a good fit for adding to Kubb so other users know that this is coming soon :)

[nmnmcc]

Thanks for the context. Waiting until after Kubb v5 works for me. I opened #706 to explain the motivation and proposed plugin split for Effect support. I'll keep this PR as a draft and rebase and update the implementation once v5 is released.