refactor: establish standalone application boundary

app/frontend/pages/ladder/page.html

@@ -0,0 +1,19 @@
+    <section id="ladderView" class="workspace-view page redesigned-ladder-view">
+      <div class="section-toolbar lad-head redesigned-page-head ladder-page-head">
+        <div class="section-title-group">
+          <h2>市场天梯</h2>
+          <span class="section-subtitle">按连板高度观察空间板与梯队完整度 · <b id="ladderDateRange">--</b></span>
+        </div>
+        <div class="ladder-head-actions">
+          <div id="ladderSortSegment" class="ladder-sort-segment" role="group" aria-label="天梯排序">
+            <button type="button" class="active" data-ladder-sort="time" aria-pressed="true">按封板时间</button>
+            <button type="button" data-ladder-sort="open" aria-pressed="false">按开板次数</button>
+          </div>
+          <button id="ladderExportButton" class="button" type="button">导出 CSV</button>
+        </div>
+      </div>
+      <div class="market-ladder-workspace lad-grid">
+        <div id="ladderBoard" class="market-ladder-board"></div>
+        <aside id="ladderInsights" class="market-ladder-insights" aria-label="天梯结构解读"></aside>
+      </div>
+    </section>

app/frontend/pages/ladder/page.js

@@ -1,6 +1,5 @@
-window.XiaobaiPageModules.register("ladder", ["ladderView"]);
+window.XiaobaiPageModules.register("ladder", ["ladderView"], { bind: bindLadderEvents });
 
-/* PRESERVATION-SOURCE-BEGIN app.js:2125-2216 */
 function renderLadderMini(ladders) {
   const container = document.querySelector("#ladderMini");
   const highest = ladders.length ? Math.max(...ladders.map((item) => number(item.level))) : 0;
@@ -93,4 +92,18 @@ function renderLadderBoard(ladders) {
   refreshIcons();
 }
 
-/* PRESERVATION-SOURCE-END app.js:2125-2216 */
+
+function bindLadderEvents() {
+  document.querySelectorAll("[data-ladder-sort]").forEach((button) => {
+    button.addEventListener("click", () => {
+      state.ladderSortMode = button.dataset.ladderSort === "open" ? "open" : "time";
+      document.querySelectorAll("[data-ladder-sort]").forEach((item) => {
+        const active = item === button;
+        item.classList.toggle("active", active);
+        item.setAttribute("aria-pressed", String(active));
+      });
+      renderLadderBoard(state.dashboard?.ladders || []);
+    });
+  });
+  document.querySelector("#ladderExportButton").addEventListener("click", exportLadder);
+}