fix: 为 Eino agentic 路径补充 tool_call/tool_result 配对防御中间件

agentic 路径(单代理模式)缺少 toolPairReconciler 和 orphanToolPruner，
当 summarization 截断历史破坏配对后，序列化到 OpenAI API 触发 400
"insufficient tool messages following tool_calls message"。

新增 AgenticMessage 版本的 reconciler 和 pruner，与 classic 路径对齐。

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/multiagent/agentic_orphan_tool_pruner_middleware.go

@@ -0,0 +1,126 @@
+package multiagent
+
+import (
+	"context"
+
+	"github.com/cloudwego/eino/adk"
+	"github.com/cloudwego/eino/schema"
+	"go.uber.org/zap"
+)
+
+// agenticOrphanToolPrunerMiddleware is the AgenticMessage equivalent of
+// orphanToolPrunerMiddleware. It removes user-role messages whose content
+// blocks are exclusively FunctionToolResult entries with CallIDs that do not
+// match any FunctionToolCall in the history.
+//
+// This is a defense-in-depth layer after agenticToolPairReconcilerMiddleware;
+// the reconciler handles the common case (assistant followed by its results)
+// while this pruner catches stray results that appear before their assistant
+// or in non-adjacent positions (e.g. after summarization rewriting).
+type agenticOrphanToolPrunerMiddleware struct {
+	*adk.TypedBaseChatModelAgentMiddleware[*schema.AgenticMessage]
+	logger *zap.Logger
+	phase  string
+}
+
+func newAgenticOrphanToolPrunerMiddleware(logger *zap.Logger, phase string) adk.TypedChatModelAgentMiddleware[*schema.AgenticMessage] {
+	return &agenticOrphanToolPrunerMiddleware{
+		TypedBaseChatModelAgentMiddleware: &adk.TypedBaseChatModelAgentMiddleware[*schema.AgenticMessage]{},
+		logger:                            logger,
+		phase:                             phase,
+	}
+}
+
+func (m *agenticOrphanToolPrunerMiddleware) BeforeModelRewriteState(
+	ctx context.Context,
+	state *adk.TypedChatModelAgentState[*schema.AgenticMessage],
+	mc *adk.TypedModelContext[*schema.AgenticMessage],
+) (context.Context, *adk.TypedChatModelAgentState[*schema.AgenticMessage], error) {
+	_ = mc
+	if m == nil || state == nil || len(state.Messages) == 0 {
+		return ctx, state, nil
+	}
+
+	// Pass 1: collect all provided CallIDs from assistant FunctionToolCall blocks.
+	provided := make(map[string]struct{}, 8)
+	for _, msg := range state.Messages {
+		if msg == nil || msg.Role != schema.AgenticRoleTypeAssistant {
+			continue
+		}
+		for _, block := range msg.ContentBlocks {
+			if block != nil && block.FunctionToolCall != nil && block.FunctionToolCall.CallID != "" {
+				provided[block.FunctionToolCall.CallID] = struct{}{}
+			}
+		}
+	}
+
+	// Fast path: check if any orphan exists.
+	hasOrphan := false
+	for _, msg := range state.Messages {
+		if msg == nil || !isPureAgenticToolResult(msg) {
+			continue
+		}
+		for _, id := range agenticToolResultCallIDs(msg) {
+			if _, ok := provided[id]; !ok {
+				hasOrphan = true
+				break
+			}
+		}
+		if hasOrphan {
+			break
+		}
+	}
+	if !hasOrphan {
+		return ctx, state, nil
+	}
+
+	// Pass 2: build pruned list.
+	pruned := make([]*schema.AgenticMessage, 0, len(state.Messages))
+	var droppedIDs []string
+	var droppedNames []string
+	for _, msg := range state.Messages {
+		if msg == nil {
+			continue
+		}
+		if !isPureAgenticToolResult(msg) {
+			pruned = append(pruned, msg)
+			continue
+		}
+		// Check if ALL result call IDs are orphans. If any is matched, keep the
+		// message (the reconciler already handled partial mismatches).
+		allOrphan := true
+		for _, id := range agenticToolResultCallIDs(msg) {
+			if _, ok := provided[id]; ok {
+				allOrphan = false
+				break
+			}
+		}
+		if allOrphan {
+			for _, block := range msg.ContentBlocks {
+				if block != nil && block.FunctionToolResult != nil {
+					droppedIDs = append(droppedIDs, block.FunctionToolResult.CallID)
+					droppedNames = append(droppedNames, block.FunctionToolResult.Name)
+				}
+			}
+			continue
+		}
+		pruned = append(pruned, msg)
+	}
+
+	if len(droppedIDs) == 0 {
+		return ctx, state, nil
+	}
+	if m.logger != nil {
+		m.logger.Warn("agentic orphan tool messages pruned before model call",
+			zap.String("phase", m.phase),
+			zap.Int("dropped_count", len(droppedIDs)),
+			zap.Strings("dropped_tool_call_ids", droppedIDs),
+			zap.Strings("dropped_tool_names", droppedNames),
+			zap.Int("messages_before", len(state.Messages)),
+			zap.Int("messages_after", len(pruned)),
+		)
+	}
+	ns := *state
+	ns.Messages = pruned
+	return ctx, &ns, nil
+}