fix(channels): check json marshal/unmarshal errors in toChannelHashes

Replace silently discarded json.Marshal and json.Unmarshal errors with
explicit checks. If serialization fails, log a warning and either
return early (for the config-level marshal/unmarshal) or skip the
channel (for per-channel marshal). This prevents silent data loss
when channel configuration contains unexpected types.

pkg/tools/toolloop.go

@@ -132,7 +132,11 @@ func RunToolLoop(
 			Content: response.Content,
 		}
 		for _, tc := range normalizedToolCalls {
-			argumentsJSON, _ := json.Marshal(tc.Arguments)
+			argumentsJSON, err := json.Marshal(tc.Arguments)
+			if err != nil {
+				logger.Warnf("toolloop: failed to marshal tool call arguments for %s: %v", tc.Name, err)
+				argumentsJSON = []byte("{}")
+			}
 			assistantMsg.ToolCalls = append(assistantMsg.ToolCalls, providers.ToolCall{
 				ID:        tc.ID,
 				Type:      "function",