chore: update dependencies and minor agent/provider fixes

- go mod tidy (clean unused deps)
- pkg/agent: minor loop adjustments
- pkg/providers: factory provider update

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pkg/agent/loop.go

@@ -2817,7 +2817,11 @@ turnLoop:
 	if finalContent == "" {
 		if ts.currentIteration() >= ts.agent.MaxIterations && ts.agent.MaxIterations > 0 {
 			finalContent = toolLimitResponse
-		} else {
+		} else if ts.currentIteration() == 0 {
+			// Only show "empty response" fallback when no tool calls were made.
+			// If the model executed tool calls but returned empty text afterward,
+			// the work was already communicated via tool results — sending a
+			// technical error message to the user is confusing and unhelpful.
 			finalContent = ts.opts.DefaultResponse
 		}
 	}

pkg/providers/factory_provider.go

@@ -342,6 +342,13 @@ func CreateProviderFromConfig(cfg *config.ModelConfig) (LLMProvider, string, err
 		}
 		return NewCodexCliProvider(workspace), modelID, nil
 
+	case "hermes-acp", "hermesacp":
+		workspace := cfg.Workspace
+		if workspace == "" {
+			workspace = "."
+		}
+		return NewHermesACPProvider(workspace), modelID, nil
+
 	case "github-copilot", "copilot":
 		apiBase := cfg.APIBase
 		if apiBase == "" {