fix(chat): 用本地任务键判断调研前置，避免越界依赖

chat 不能引用 workflowdef。调研报告只认 research 与 bd_research 两个现用键。

internal/chat/workflow_guidance.go

@@ -9,7 +9,6 @@ import (
 	"chat-agent-system/internal/coordinator"
 	"chat-agent-system/internal/docgov"
 	"chat-agent-system/internal/intent"
-	"chat-agent-system/internal/workflowdef"
 )
 
 const stageAdvanceGuidance = "该文档所属阶段尚未激活。请先完成当前阶段并推进后再编制。"
@@ -36,9 +35,18 @@ func workflowPrerequisiteHint(userInput string, docs []docgov.WorkflowDocumentSu
 	return researchFirstHint, key
 }
 
+func isResearchTaskKey(key string) bool {
+	switch strings.TrimSpace(key) {
+	case "research", "bd_research":
+		return true
+	default:
+		return false
+	}
+}
+
 func researchMaterialReady(docs []docgov.WorkflowDocumentSummary) (ready bool, taskKey string) {
 	for _, doc := range docs {
-		if !workflowdef.SameTaskKey(doc.TaskKey, "research") {
+		if !isResearchTaskKey(doc.TaskKey) {
 			continue
 		}
 		taskKey = doc.TaskKey