Split src/data2dsl_adapters.py (~1796 lines, 25 classes) into focused
submodules by adapter family while preserving the public data2dsl_adapters
import surface (facade re-exports).
Addresses Koru planfile ticket STARTER-061.
data2dsl_adapters_<family>.py.data2dsl_adapters.py remains a stable facade with __all__.pyproject.toml lists every new standalone module.main.