feat: complete 294/294 libretro core profiling

Final batch: stonesoup, vitaquake3+vitavoyager, uw8, uxn, wasm4,
tempgba, retro8, moonlight, ffmpeg, imageviewer, mpv, remotejoy,
puzzlescript, lutro, mojozork, simcp (SAM Coupe, ROM built-in),
romcleaner, redbook, onsyuri, mcsoftserve, x64sdl (VICE alias)

204 total emulator/core profiles covering ALL 294 libretro cores.
Every core analyzed from source code. Complete museum documentation.

emulators/ffmpeg.yml

@@ -0,0 +1,16 @@
+emulator: FFmpeg
+type: utility
+source: "https://github.com/libretro/RetroArch"
+cores:
+  - ffmpeg
+systems: []
+
+notes: |
+  FFmpeg core is a media player built into RetroArch using libavcodec,
+  libavformat, and libswscale. Plays video and audio files directly
+  within the RetroArch interface.
+
+  No BIOS or system files required. Codec support depends on the
+  FFmpeg libraries linked at build time.
+
+files: []