feat: separate frozen snapshot profiles, fix shared cores

Created desmume2015.yml with files: [] (code doesn't load BIOS).
Removed desmume2015 from desmume.yml cores list.
Removed cdi2015 from same_cdi.yml (separate profile exists).

Frozen snapshots must have their own profiles because their
firmware behavior differs from the current version.

emulators/desmume.yml

@@ -4,7 +4,7 @@ source: "https://github.com/libretro/desmume"
 profiled_date: "2026-03-18"
 core_version: "SVN"
 display_name: "Nintendo - DS (DeSmuME)"
-cores: [desmume, desmume2015]
+cores: [desmume]
 systems: [nintendo-ds]
 
 notes: |

emulators/desmume2015.yml

@@ -0,0 +1,17 @@
+emulator: DeSmuME 2015
+type: libretro
+source: "https://github.com/libretro/desmume2015"
+profiled_date: "2026-03-19"
+core_version: "SVN (2015 snapshot)"
+display_name: "Nintendo - DS (DeSmuME 2015)"
+cores: [desmume2015]
+systems: [nintendo-ds]
+
+notes: |
+  Frozen 2015 snapshot of DeSmuME. The external BIOS loading feature
+  (desmume_use_external_bios) does NOT exist in this version.
+  The .info declares firmware_count=3 but the code never loads them.
+  Verified: libretro.cpp has no bios7/bios9/firmware path construction.
+  ref: desmume2015/desmume/src/frontend/libretro/libretro.cpp
+
+files: []

emulators/same_cdi.yml

@@ -1,6 +1,6 @@
 emulator: SAME CDi
 type: libretro
-cores: [same_cdi, cdi2015]
+cores: [same_cdi]
 source: "https://github.com/libretro/same_cdi"
 profiled_date: "2026-03-18"
 core_version: "Git"