Move 17 case-colliding BIOS variants to .variants/ so Windows
and macOS clones no longer lose files. Existence-based platforms
keep the primary, MD5-based platforms resolve from .variants/.
Also fix resolve_local_file zipped_file resolution: when multiple
ZIPs share a name, verify the inner ROM exists before accepting
a candidate. Fixes adam_fdc.zip resolving to the wrong archive.
27df5c8fb5
