✨ feat(vscode): state JSON 新增 handoffAttachmentId/handoffFrom，Issue 透出 assignees

Claude-Session: https://claude.ai/code/session_011cEyL6k351U2BzX1Qmygph

vscode/cli/cmd/spx/main.go

@@ -408,6 +408,8 @@ var knownStateFields = map[string]struct{}{
 	"implementStatus":       {},
 	"color":                 {},
 	"autoReview":            {},
+	"handoffAttachmentId":   {},
+	"handoffFrom":           {},
 }
 
 // parseStateComment returns the parsed map when body is a JSON object carrying