Auto-Context: Semantische Kontext-Injektion, Memory-File-Embeddings, Agent-Toggle

- Automatische Embedding-basierte Kontext-Injektion vor jeder API-Anfrage
  (Top 5 Chat-Ergebnisse + Top 3 Memory-File-Treffer als recalled_context)
- Memory-Dateien (.md) werden embedded (Backfill + Live nach memory_write)
- Neue Agent-Option 'useAutoContext' (Checkbox, Default: aktiviert)
- VectorSearchService: SearchMemoryFilesAsync, EmbedMemoryFileAsync, Chunking
- EmbeddingBackgroundService: Memory-File-Backfill + EnqueueMemoryFile
- ToolService: memory_write löst Re-Embedding aus
- embeddingBg Parameter an ExecuteTool durchgereicht

Endpoints/AgentEndpoint.cs

@@ -64,6 +64,7 @@ public static class AgentEndpoint
                 a.UseIdentity,
                 a.UseUserInfo,
                 a.UseMemory,
+                a.UseAutoContext,
                 a.UseWebSearch,
                 a.WebSearchVersion,
                 a.AllowUserChoice,
@@ -119,6 +120,7 @@ public static class AgentEndpoint
             UseIdentity = !body.TryGetProperty("useIdentity", out var ui) || ui.GetBoolean(),
             UseUserInfo = !body.TryGetProperty("useUserInfo", out var uu) || uu.GetBoolean(),
             UseMemory = !body.TryGetProperty("useMemory", out var um) || um.GetBoolean(),
+            UseAutoContext = !body.TryGetProperty("useAutoContext", out var uac) || uac.GetBoolean(),
             UseWebSearch = body.TryGetProperty("webSearchVersion", out var wsv) && !string.IsNullOrEmpty(wsv.GetString()),
             WebSearchVersion = body.TryGetProperty("webSearchVersion", out var wsv2) ? wsv2.GetString() ?? "" : "",
             AllowUserChoice = !body.TryGetProperty("allowUserChoice", out var auc) || auc.GetBoolean(),
@@ -160,6 +162,7 @@ public static class AgentEndpoint
         if (body.TryGetProperty("useIdentity", out var ui)) agent.UseIdentity = ui.GetBoolean();
         if (body.TryGetProperty("useUserInfo", out var uu)) agent.UseUserInfo = uu.GetBoolean();
         if (body.TryGetProperty("useMemory", out var um)) agent.UseMemory = um.GetBoolean();
+        if (body.TryGetProperty("useAutoContext", out var uac)) agent.UseAutoContext = uac.GetBoolean();
         if (body.TryGetProperty("webSearchVersion", out var wsv))
         {
             agent.WebSearchVersion = wsv.GetString() ?? "";