refactor: migrate to CreatePromise pattern and introduce KV worker
- Migrated wasm/ files to CreatePromise w/ proper async handling
- New KV worker architecture replacing state worker
- Created internal jsutil/ package replacing wasm-utils dependency
- Migrated to goccy/go-json for WASM performance
- Standardized error handling with JavaScript Error objects
- Upgraded Go 1.21 → 1.25.3
- Removed state worker
- Use modern, unmodified wasm_exec, so we don't have upgrade pain moving forward.