feat: hle_fallback on 39 emulator profiles (266 entries)

Batch analysis of all 273 profiles to identify HLE/embedded
fallbacks. Added hle_fallback: true where the core has verified
software replacement for missing BIOS files:

- Embedded ROMs: vice (102), ep128emu (22), fuse (18), frodo (4)
- HLE BIOS: bsnes* (33 across 3 profiles), puae (9 AROS),
  noods (4), melonds* (6 FreeBIOS), flycast (3 reios)
- Open-source replacements: sameboy (8), pokemini (1), gpsp (1)
- Built-in fallbacks: np2kai (7), atari800 (6 Altirra),
  picodrive (3), quasi88 (4), gambatte (2)

Conservative: only added where notes or source code confirm HLE.
Skipped 50+ profiles where files are optional alternatives, not
HLE replaceable (neocd, opera, kronos, pcem, etc.)

emulators/prosystem.yml

@@ -29,6 +29,7 @@ files:
   - name: "7800 BIOS (U).rom"
     system: atari-7800
     required: false
+    hle_fallback: true
     size: 4096  # 4 KB
     note: "NTSC/US Atari 7800 BIOS. Loaded when cartridge_region != REGION_PAL."
     source_ref: "core/libretro.c:585"
@@ -36,6 +37,7 @@ files:
   - name: "7800 BIOS (E).rom"
     system: atari-7800
     required: false
+    hle_fallback: true
     size: 16384  # 16 KB (PAL BIOS is larger than NTSC)
     note: "PAL/EU Atari 7800 BIOS. Loaded when cartridge_region == REGION_PAL."
     source_ref: "core/libretro.c:583"