Gate empty-result warnings on true empty runs

crates/bt-demo/src/main.rs

@@ -433,12 +433,12 @@ fn build_warnings(
     if holdings.is_empty() {
         warnings.push("期末没有持仓。".to_string());
     }
-    if diagnostics
+    let selected_after_ma_is_empty = diagnostics
         .get("selected_after_ma")
         .and_then(|v| v.as_i64())
         .unwrap_or(0)
-        == 0
-    {
+        == 0;
+    if selected_after_ma_is_empty && fills.is_empty() && holdings.is_empty() {
         warnings
             .push("最终没有股票通过完整选股链路，结果为空时请优先查看 diagnostics。".to_string());
     }