Improve story summary assembly and UI

modules/story-summary/data/store.js

@@ -31,9 +31,12 @@ export function getKeepVisibleCount() {
     return store?.keepVisibleCount ?? 3;
 }
 
-export function calcHideRange(lastSummarized) {
+// boundary：隐藏边界（由调用方决定语义：LLM总结边界 or 向量边界）
+export function calcHideRange(boundary) {
+    if (boundary == null || boundary < 0) return null;
+
     const keepCount = getKeepVisibleCount();
-    const hideEnd = lastSummarized - keepCount;
+    const hideEnd = boundary - keepCount;
     if (hideEnd < 0) return null;
     return { start: 0, end: hideEnd };
 }
@@ -285,4 +288,4 @@ export async function clearSummaryData(chatId) {
 export function getWorldSnapshot() {
     const store = getSummaryStore();
     return store?.json?.world || [];
-}
+}