fix(nav): .nav-more-wrap contain:layout — open dropdown inflated parent flex line, clipped nav offscreen (#1406)

ACTUAL root cause of the recurring nav-vanishing bug, validated live via
Chrome CDP probe on staging at vw=1030.

## What happens

When the More dropdown opens:
- BEFORE: nav_links.y = 2.67, nav_left.scrollHeight = 47, nav visible ✅
- OPEN: nav_links.y = -46.67, nav_left.scrollHeight = 279, nav clipped
offscreen ❌

The .nav-more-menu is position:absolute but its content extents inflate
.nav-more-wrap.scrollHeight. .nav-left { display:flex;
align-items:center } then centers a 279px content line in a 52px
container, putting everything above the visible band.

## Fix

Add contain:layout to .nav-more-wrap — isolates its layout box from the
parent flex calculation. No more bubble-up.

CDP verification with the fix applied: dropdown opens, all 6 items
render at proper y (56, 93, 130, 166, 203, 240), nav_links_y stays at
2.67, nav_left.scrollHeight stays at 47.

## Why prior 22 fixes didn't catch it

Every prior fix treated symptoms — Priority+ algorithm tweaks, overflow
flag toggles, min-height drops, etc. None instrumented the CLOSED→OPEN
state transition that reveals the flex-line bug. Required Chrome
DevTools Protocol on a real broken viewport to see the inflate happen
live.

Fixes #1406 and likely supersedes #1391, #1396, #1400, #1404.

Co-authored-by: openclaw-bot <bot@openclaw.local>

public/app.js

@@ -1348,9 +1348,19 @@ window.addEventListener('DOMContentLoaded', () => {
       requestAnimationFrame(applyNavPriority);
     });
 
+    // #1406: position the fixed dropdown relative to the More button on each open.
+    // Required because .nav-more-menu is position:fixed (so it escapes
+    // .nav-more-wrap's layout box and doesn't inflate the parent flex line).
+    function positionMoreMenu() {
+      var wr = navMoreWrap.getBoundingClientRect();
+      navMoreMenu.style.top = (wr.bottom + 4) + 'px';
+      navMoreMenu.style.right = (window.innerWidth - wr.right) + 'px';
+      navMoreMenu.style.left = 'auto';
+    }
     navMoreBtn.addEventListener('click', (e) => {
       e.stopPropagation();
       const opening = !navMoreMenu.classList.contains('open');
+      if (opening) positionMoreMenu();
       navMoreMenu.classList.toggle('open');
       navMoreBtn.setAttribute('aria-expanded', String(opening));
       if (opening) {
@@ -1358,6 +1368,10 @@ window.addEventListener('DOMContentLoaded', () => {
         if (firstLink) firstLink.focus();
       }
     });
+    // Re-position on window resize while open.
+    window.addEventListener('resize', () => {
+      if (navMoreMenu.classList.contains('open')) positionMoreMenu();
+    });
   }
 
   document.addEventListener('keydown', (e) => {

public/style.css

@@ -1691,8 +1691,14 @@ button.ch-item:hover .ch-icon-btn { opacity: 1; }
 /* "More" button (hidden on desktop) */
 .nav-more-wrap { display: none; position: relative; }
 .nav-more-btn { display: inline-flex; }
+/* #1406: position:fixed (not absolute) so the dropdown escapes .nav-more-wrap's
+   layout box. When absolute, the dropdown's content extents inflated
+   .nav-more-wrap.scrollHeight → bubbled into .nav-left flex line-height calc
+   → centered a 279px content line in 52px container → entire nav strip clipped
+   above viewport. position:fixed removes the dropdown from flow entirely; JS in
+   app.js positions top/right dynamically relative to the More button. */
 .nav-more-menu {
-  display: none; position: absolute; top: calc(var(--top-nav-h, 52px) - 4px); right: 0;
+  display: none; position: fixed; right: 0; top: 0;
   background: var(--nav-bg); border: 1px solid var(--border); border-radius: 8px;
   box-shadow: 0 4px 12px rgba(0,0,0,0.15); flex-direction: column;
   min-width: 160px; padding: 4px 0; z-index: 1200;