Remove tool_choice agent option - auto-detect based on workspace/skills/memory

- Remove tool_choice from AgentEndpoint (create, update, list responses)
- ChatService: automatically set tool_choice='any' when workspace, memory
  or skills present, null otherwise. Same for preparer/review/finalizer
- SystemPromptBuilder: remove 3 toolAny-conditional prompt blocks
  (KRITISCH, Verhalten, ERINNERUNG)
- Frontend: remove checkbox, badge and JS references
- Agent.ToolChoice DB field preserved for backward compat, no longer read

Endpoints/AgentEndpoint.cs

@@ -46,7 +46,6 @@ public static class AgentEndpoint
                 Avatar = a.AvatarSmall ?? a.Avatar,
                 a.Description,
                 a.Model,
-                a.ToolChoice,
                 a.CustomCommands,
                 a.AutoCommit,
                 a.UseSoul,
@@ -94,7 +93,6 @@ public static class AgentEndpoint
                 Avatar = a.AvatarSmall ?? a.Avatar,
                 a.Description,
                 a.Model,
-                a.ToolChoice,
                 a.CustomCommands,
                 a.AutoCommit,
                 a.UseSoul,
@@ -150,7 +148,6 @@ public static class AgentEndpoint
             AvatarSmall = imageService.ResizeDataUrlSmall(avatarRaw),
             Description = body.TryGetProperty("description", out var d) ? d.GetString() : null,
             Model = body.TryGetProperty("model", out var m) ? m.GetString() ?? "sonnet" : "sonnet",
-            ToolChoice = body.TryGetProperty("toolChoice", out var tc) ? tc.GetString() ?? "any" : "any",
             CustomCommands = customCommands,
             AutoCommit = body.TryGetProperty("autoCommit", out var ac) ? ac.GetString() ?? "" : "",
             UseSoul = !body.TryGetProperty("useSoul", out var us) || us.GetBoolean(),
@@ -191,7 +188,6 @@ public static class AgentEndpoint
         }
         if (body.TryGetProperty("description", out var d)) agent.Description = d.GetString();
         if (body.TryGetProperty("model", out var m)) agent.Model = m.GetString();
-        if (body.TryGetProperty("toolChoice", out var tc)) agent.ToolChoice = tc.GetString();
         if (body.TryGetProperty("customCommands", out var cc))
             agent.CustomCommands = cc.ValueKind == JsonValueKind.Null ? null : cc.GetRawText();
         if (body.TryGetProperty("autoCommit", out var ac)) agent.AutoCommit = ac.GetString() ?? "";