A copy under .variants/ exists to hold a content its primary does
not. 29 held bytes another file already carried, under a second or
third identity: msx.rom and MSX.ROM variants equal to
MSX_8020-20bios.rom, naomi2.zip.da79eca4 whose suffix named the
primary's sha1 rather than its own. dedup now removes such a copy,
keeping one when only variants hold the content. The LaserActive
PAC-S10 BIOS lived only under .variants/ while RetroBat names it
without a hash; it moves beside its siblings.
Source: Subtixx/RetroStation MSX2J.rom
SHA256 0c672d86 matches ares desktop-ui/emulator/msx2.cpp:15.
Resolves last MSX2.ROM discrepancy across all platforms.
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.
Abdessamad Derraz