Merge main (gene system G1-G5, phases C-D) into the multiplayer branch

Main independently adopted the engine Core/Host split in G1, so the
scene adaptations conflicted with identical changes here — resolved in
main's favor (its scenes also carry the gene-driven world). Kept from
this branch: BootScene's --connect path into MultiplayerScene, the
buildAtlases switch in GameContent.Load (with the Task.Run lambda fix
its optional parameter requires), net.* localization keys, and the
Net/Server/Web projects in the solution. Program.cs now has both CLI
modes: --check-content (main) and --connect (here). The engine pointer
lands on d044caf, which linearly contains both lines of work.

Verified on the merged tree: 366 engine tests pass, --check-content
reports genes/traits intact, and a live --listen server replicates
moving pawns to the probe.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Mods/Core/Textures/things/pawn/animal/guineapig/AEXP_GuineaPig_SkinSet.xml

@@ -1,7 +1,6 @@
 <?xml version="1.0" encoding="utf-8" ?>
 
 <SkinSet>
-  
   <lifeStage>
     <appliesToAll>true</appliesToAll>
     <variants>
@@ -9,24 +8,21 @@
         <commonality>0</commonality>
         <texName>GuineaPig</texName>
       </skin>
-      
+
       <skin>
         <commonality>0.4</commonality>
         <texName>GuineaPig1</texName>
       </skin>
-      
+
       <skin>
         <commonality>0.4</commonality>
         <texName>GuineaPig2</texName>
       </skin>
-      
+
       <skin>
         <commonality>0.4</commonality>
         <texName>GuineaPig3</texName>
       </skin>
-      
-      
-    </variants>  
+    </variants>
   </lifeStage>
-  
 </SkinSet>

Mods/Core/Textures/things/pawn/animal/horse/AEXP_Horse_SkinSet.xml

@@ -1,7 +1,6 @@
 <?xml version="1.0" encoding="utf-8" ?>
 
 <SkinSet>
-  
   <lifeStage>
     <appliesToAll>true</appliesToAll>
     <variants>
@@ -9,38 +8,36 @@
         <commonality>0.12</commonality>
         <texName>Horse</texName>
       </skin>
-      
+
       <skin>
         <commonality>0.25</commonality>
         <texName>Horse1</texName>
       </skin>
-      
+
       <skin>
         <commonality>0.4</commonality>
         <texName>Horse2</texName>
       </skin>
-      
+
       <skin>
         <commonality>0.4</commonality>
         <texName>Horse3</texName>
       </skin>
-      
+
       <skin>
         <commonality>0.4</commonality>
         <texName>Horse4</texName>
       </skin>
-      
+
       <skin>
         <commonality>0.35</commonality>
         <texName>Horse5</texName>
       </skin>
-      
+
       <skin>
         <commonality>0.25</commonality>
         <texName>Horse6</texName>
       </skin>
-      
-    </variants>  
+    </variants>
   </lifeStage>
-  
 </SkinSet>