fix(reasoning): persist canonical history for DeepSeek and web chat

pkg/providers/messageutil/messageutil.go

@@ -0,0 +1,41 @@
+package messageutil
+
+import (
+	"strings"
+
+	"github.com/sipeed/picoclaw/pkg/providers/protocoltypes"
+)
+
+// IsTransientAssistantThoughtMessage reports whether msg is an invalid
+// reasoning-only assistant history record. These "hanging" thought messages
+// are not a canonical persisted format and should be discarded instead of
+// replayed or reconstructed.
+func IsTransientAssistantThoughtMessage(msg protocoltypes.Message) bool {
+	return msg.Role == "assistant" &&
+		strings.TrimSpace(msg.Content) == "" &&
+		strings.TrimSpace(msg.ReasoningContent) != "" &&
+		len(msg.ToolCalls) == 0 &&
+		len(msg.Media) == 0 &&
+		len(msg.Attachments) == 0 &&
+		strings.TrimSpace(msg.ToolCallID) == ""
+}
+
+// FilterInvalidHistoryMessages removes invalid persisted history records such
+// as transient assistant thought-only messages.
+func FilterInvalidHistoryMessages(history []protocoltypes.Message) []protocoltypes.Message {
+	if len(history) == 0 {
+		return []protocoltypes.Message{}
+	}
+
+	filtered := make([]protocoltypes.Message, 0, len(history))
+	for _, msg := range history {
+		if IsTransientAssistantThoughtMessage(msg) {
+			continue
+		}
+		filtered = append(filtered, msg)
+	}
+	if filtered == nil {
+		return []protocoltypes.Message{}
+	}
+	return filtered
+}