Add support for extension private deps

src/Core/ExtensionsManager.cs

@@ -4,9 +4,36 @@
 using SwarmUI.Utils;
 using System.IO;
 using System.Reflection;
+using System.Runtime.Loader;
 
 namespace SwarmUI.Core;
 
+public class SwarmExtensionLoadContext(string name, string extensionDir) : AssemblyLoadContext(name, isCollectible: false)
+{
+    /// <summary>Host wins, then we probe the extension's folder for private deps.</summary>
+    protected override Assembly Load(AssemblyName name)
+    {
+        string candidate = Path.Combine(extensionDir, name.Name + ".dll");
+        // Host wins to keep type identity intact. If the extension also shipped its own copy, that's almost always a csproj misconfig (missing Private=false), so warn.
+        try
+        {
+            Default.LoadFromAssemblyName(name);
+            if (File.Exists(candidate))
+            {
+                Logs.Warning($"Extension {Name} ships {name.Name}.dll but host already has it; using host copy. Set Private=false on that reference.");
+            }
+            return null;
+        }
+        catch (FileNotFoundException) { }
+        if (!File.Exists(candidate))
+        {
+            return null;
+        }
+        Logs.Debug($"Extension {Name} loading private dep {name.Name} from {candidate}");
+        return LoadFromAssemblyPath(candidate);
+    }
+}
+
 public class ExtensionsManager
 {
     /// <summary>All extensions currently loaded.</summary>
@@ -45,6 +72,15 @@ public static HtmlString HtmlTags(string[] tags)
     /// <summary>List of known online available extensions.</summary>
     public List<ExtensionInfo> KnownExtensions = [];
 
+    /// <summary>Per-extension load contexts, keyed by extension DLL name. Each extension gets its own <see cref="SwarmExtensionLoadContext"/> so private dependencies stay isolated from other extensions.</summary>
+    public ConcurrentDictionary<string, SwarmExtensionLoadContext> ExtensionLoadContexts = new();
+
+    private Assembly LoadInExtensionContext(string dllName, string targetPath)
+    {
+        SwarmExtensionLoadContext ctx = ExtensionLoadContexts.GetOrAdd(dllName, n => new SwarmExtensionLoadContext(n, Path.GetDirectoryName(targetPath)));
+        return ctx.LoadFromAssemblyPath(targetPath);
+    }
+
     public static string ReferenceCsproj =
         """
         <Project Sdk="Microsoft.NET.Sdk.Web">
@@ -181,7 +217,7 @@ public async Task<Assembly> BuildExtension(string folder, string projFile)
         if (File.Exists(target) && !Program.IsDevMode)
         {
             Logs.Debug($"Don't need to rebuild extension {projFile}, already built.");
-            return Assembly.LoadFile(Path.GetFullPath(target));
+            return LoadInExtensionContext(dllName, Path.GetFullPath(target));
         }
         Logs.Debug($"Building extension project: {projFile}...");
         string buildParam = $"-p:BaseIntermediateOutputPath={Path.GetFullPath($"./src/obj/extensions/{dllName}/")};TargetName={dllName}-{hash}";
@@ -195,7 +231,7 @@ public async Task<Assembly> BuildExtension(string folder, string projFile)
         {
             Logs.Debug($"Successful build output for extension project {projFile}:\n{output}");
         }
-        return Assembly.LoadFile(Path.GetFullPath(target));
+        return LoadInExtensionContext(dllName, Path.GetFullPath(target));
     }
 
     public void PrepExtension(Type extType, bool isCore, string[] possible)