feat: surface auto project sync guidance in master chat

src/lib/boss-data.ts

@@ -6233,6 +6233,17 @@ export async function completeMasterAgentTask(payload: {
               body: buildProjectUnderstandingUpdateDigest(targetProject.name, understanding),
               kind: "system_notice",
             });
+            if (
+              understanding.recommendedNextStep?.trim() &&
+              previousUnderstanding?.recommendedNextStep !== understanding.recommendedNextStep
+            ) {
+              pushProjectLedgerMessage(state, "master-agent", {
+                sender: "master",
+                senderLabel: "主 Agent",
+                body: buildProjectUnderstandingNextStepNotice(targetProject.name, understanding),
+                kind: "system_notice",
+              });
+            }
             publishBossEvent("project.messages.updated", { projectId: "master-agent" });
             publishBossEvent("conversation.updated", { projectId: "master-agent" });
           }
@@ -7396,6 +7407,12 @@ function buildProjectUnderstandingUpdateDigest(projectName: string, snapshot: Pr
     .join("\n");
 }
 
+function buildProjectUnderstandingNextStepNotice(projectName: string, snapshot: ProjectUnderstandingSnapshot) {
+  return [`建议下一步推进：${projectName}`, snapshot.recommendedNextStep?.trim() || ""]
+    .filter(Boolean)
+    .join("\n");
+}
+
 function shouldQueueProjectUnderstandingSync(project: Project, observedActivityAt: string, state: BossState) {
   if (!isDispatchableThreadProject(project)) {
     return false;