Forge build merges client mixins into common section, crashing dedicated servers

[MauveAvenger]

Bug Description

The Forge build does not preserve the "client" section in
playerengine.mixins.json. Client-only mixins are merged into the main
"mixins" array, causing dedicated servers to crash.

Source vs Built Jar

Source (common/src/main/resources/playerengine.mixins.json):

"client": [                                                                   
  "ClientBlockBreakMixin",                                                    
  "ClientConnectionAccessor",                                                 
  "PlayerCollidesWithEntityMixin"                                             
],                                                                            
"mixins": [                                                                   
  "EntityAccessor",                                                           
  ...                                                                         
]                                                                             
                                                                              
Built Forge Jar (after build):                                                
"client": [],                                                                 
"mixins": [                                                                   
  "ClientBlockBreakMixin",      // <-- should be client only!                 
  "ClientConnectionAccessor",   // <-- should be client only!                 
  "PlayerCollidesWithEntityMixin", // <-- should be client only!              
  "EntityAccessor",                                                           
  ...                                                                         
]                                                                             
                                                                              
Crash Log                                                                     
                                                                              
[main/FATAL] [mixin/]: Mixin apply for mod playerengine failed                
playerengine.mixins.json:PlayerCollidesWithEntityMixin from mod playerengine  
-> net.minecraft.world.entity.player.Player: InvalidMixinException            
ClassMetadataNotFoundException ... net/minecraft/client/player/LocalPlayer    
                                                                              
Environment                                                                   
                                                                              
- Minecraft 1.20.1                                                            
- Forge 47.4.0                                                                
- PlayerEngine 1.0.0                                                          
                                                                              
Suggested Fix                                                                 
                                                                              
Either use @Environment(EnvType.CLIENT) annotations on client mixins, or      
ensure the Architectury/Loom build preserves the client/server mixin          
separation.