fix(frontend): 终端弹框适配与审计实时监控布局优化

- 修复 LiveMonitorDialog 连接中卡死：WebSocket 先连、延后挂载 xterm
- 审计实时监控弹框对齐 WebSSH 布局：92vw 宽、520px 高、支持全屏
- 修复服务器终端弹框右侧黑边：fit 后同步 PTY resize，延迟二次 fit
- 抽取 xterm-utils 公共适配逻辑，统一 ResizeObserver 处理

frontend/src/lib/xterm-utils.ts

@@ -0,0 +1,66 @@
+import type { Terminal as XTerm } from 'xterm';
+import type { FitAddon } from 'xterm-addon-fit';
+
+/** FitAddon 适配终端并同步远端 PTY 尺寸（WebSSH resize） // Logan.Li */
+export function fitTerminal(fit: FitAddon, term: XTerm, ws?: WebSocket | null) {
+  fit.fit();
+  if (ws?.readyState === WebSocket.OPEN) {
+    const { cols, rows } = term;
+    ws.send(JSON.stringify({ status: 1, cols, rows }));
+  }
+}
+
+/** 等待容器就绪后挂载 xterm，并延迟二次 fit 消除右侧黑边 // Logan.Li */
+export function mountXterm(
+  term: XTerm,
+  fit: FitAddon,
+  getContainer: () => HTMLDivElement | null,
+  ws?: WebSocket | null,
+) {
+  const applyFit = () => {
+    try {
+      fitTerminal(fit, term, ws);
+      term.focus();
+    } catch {
+      /* noop */
+    }
+  };
+
+  const tryMount = () => {
+    const el = getContainer();
+    if (!el) {
+      requestAnimationFrame(tryMount);
+      return;
+    }
+    term.open(el);
+    requestAnimationFrame(applyFit);
+    setTimeout(applyFit, 100);
+  };
+
+  tryMount();
+}
+
+/** ResizeObserver 监听容器尺寸，持续 fit // Logan.Li */
+export function attachTerminalResize(
+  container: HTMLDivElement,
+  fit: FitAddon,
+  term: XTerm,
+  ws?: WebSocket | null,
+) {
+  let timer: ReturnType<typeof setTimeout>;
+  const ro = new ResizeObserver(() => {
+    clearTimeout(timer);
+    timer = setTimeout(() => {
+      try {
+        fitTerminal(fit, term, ws);
+      } catch {
+        /* noop */
+      }
+    }, 60);
+  });
+  ro.observe(container);
+  return () => {
+    clearTimeout(timer);
+    ro.disconnect();
+  };
+}