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;

tests/device-import-draft.test.ts

@@ -617,6 +617,13 @@ test("imported thread projects queue hidden understanding sync tasks on newer ac
       /实时状态同步和 UI 联调阶段/.test(message.body),
   );
   assert.ok(syncNotice, "expected master-agent conversation to receive a lightweight sync digest");
+  const nextStepNotice = masterAgentProject?.messages.findLast(
+    (message) =>
+      message.kind === "system_notice" &&
+      /建议下一步推进：智能看板主线程/.test(message.body) &&
+      /优先压平实时状态刷新抖动，再验证群聊调度链路。/.test(message.body),
+  );
+  assert.ok(nextStepNotice, "expected master-agent conversation to receive a lightweight next-step suggestion");
 });
 
 test("heartbeat candidates no longer auto-create chat windows from legacy projects when import draft is present", async () => {