fix(mysql): correct binary/varbinary types to Buffer + tests

[Iceshen87]

Description

This PR fixes the MySQL binary and varbinary column types to correctly return Buffer instead of string, along with comprehensive test coverage.

Changes

Fixed

• drizzle-orm/src/mysql-core/columns/binary.ts: Correct return type to Buffer
• drizzle-orm/src/mysql-core/columns/varbinary.ts: Correct return type to Buffer
• drizzle-orm/src/mysql-core/columns/custom.ts: Enhanced custom type handling
• drizzle-orm/src/query-builders/select.types.ts: Fixed type inference for nested selects

Added Tests

• binary.test.ts: Comprehensive tests for binary/varbinary Buffer types
• custom-select.test.ts: Tests for custom column type selection
• custom-wrap.test.ts: Tests for custom column type wrapping
• nested-select.test.ts: Tests for nested select queries

Testing

All tests pass:

• Binary/Varbinary types now correctly return Buffer
• Custom type selection works as expected
• Nested select queries maintain proper typing

Related Issues

Fixes issues with MySQL binary data handling where data was incorrectly returned as string instead of Buffer.

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/claim for Algora bounty if applicable

[Iceshen87]

✅ PR created with comprehensive fixes and test coverage.

Summary:

• Fixed MySQL binary/varbinary types to return Buffer instead of string
• Added 4 test files with 658 lines of changes
• All tests passing

Files Changed:

• drizzle-orm/src/mysql-core/columns/binary.ts
• drizzle-orm/src/mysql-core/columns/varbinary.ts
• drizzle-orm/src/mysql-core/columns/custom.ts
• drizzle-orm/src/query-builders/select.types.ts
• • 4 new test files

Ready for review! 🚀

/claim

[Iceshen87]

Hi! Thanks for reviewing this PR. I noticed it doesn't have a bounty label. Does Drizzle ORM offer bounties for bug fixes? If so, could you please add the appropriate bounty label? Thanks for your time!