fix: revert type re-exports from ORM indexes, restore migrate-client entry point

[pyramation]

Summary

The previous revert of commit d0c5a9f74 ("types") only fixed the codegen template but missed two things:

1. 9 already-generated ORM index files still had export * from './types' and export type { ConnectionResult, PageInfo } from './select-types' — causing ~80+ TS2308 name collision errors at build time
2. sdk/migrate-client/src/index.ts was deleted in that same commit and never restored — causing tsc to fail with "No inputs were found in config file"

This PR removes the leftover export * from './types' lines from all 9 generated ORM index files (constructive-cli, constructive-react, migrate-client) and restores the deleted migrate-client entry point.

Review & Testing Checklist for Human

• Run pnpm build from repo root — should complete with zero errors (previously failed on sdk/migrate-client and any package importing from ORM barrels)
• Verify the codegen template (graphql/codegen/src/core/codegen/orm/client-generator.ts) does NOT contain export * from './types' — this was fixed in a prior revert and is not part of this diff, but confirms future regenerations will be correct
• Spot-check that sdk/migrate-client/src/index.ts content (export * from './migrate') matches what existed before d0c5a9f74

Notes

• The export * from './types' approach was fundamentally broken: input-types.ts contains 2000+ generated types that collide with names in select-types.ts and shared hooks types. This cannot be fixed with explicit re-exports at scale.
• The types.ts barrel file still exists in each ORM directory and remains importable directly — it's just not re-exported through the main ORM index to avoid collisions.
• These are generated files, but the codegen template was already corrected, so future regenerations will not reintroduce these lines.

Link to Devin session: https://app.devin.ai/sessions/ce1b2dafd42341bea5d7793b0c05ba6c
Requested by: @pyramation

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