feat: add media_capabilities to provider definitions (#18)

providers/minimax.toml

@@ -8,6 +8,12 @@ display_name = "MiniMax"
 api_key_env = "MINIMAX_API_KEY"
 base_url = "https://api.minimax.io/v1"
 key_required = true
+media_capabilities = [
+  "image_generation",
+  "text_to_speech",
+  "video_generation",
+  "music_generation",
+]
 
 [provider.regions.china]
 base_url = "https://api.minimaxi.com/v1"