fix(ui): route tasks.js + skills.js dropdowns through topPortalZ() (#4768)

Fixes #4767. #4724 routed 16 body-portaled dropdowns through the shared
topPortalZ() helper so they always render just above the currently-raised tool
modal, but two were missed and still used a hardcoded z-index, so they hit the
same #4720 bug once a modal's bring-to-front counter climbed past the literal:

  - tasks.js _showTaskDropdown(): inline z-index:100000 on .task-dropdown
  - skills.js kebab menu (.skill-kebab-menu): z-index:100002 in style.css

Both now set zIndex from topPortalZ() after they are appended to the body,
matching the other migrated sites. The dead CSS z-index on .skill-kebab-menu is
removed (the inline value always wins). test_portal_dropdown_z_js.py gains a
source guard asserting both files use topPortalZ() and that no hardcoded
100000/100002 portal literal survives in either file or style.css.

static/js/skills.js

@@ -8,6 +8,7 @@
 import uiModule from './ui.js';
 import * as spinnerModule from './spinner.js';
 import { bindMenuDismiss, dismissOrRemove } from './escMenuStack.js';
+import { topPortalZ } from './toolWindowZOrder.js';
 
 const API = window.location.origin;
 let skills = [];
@@ -437,6 +438,10 @@ function _openSkillMenu(btn, card, sk, name, isPublished) {
   menu.appendChild(cancelItem);
 
   document.body.appendChild(menu);
+  // Override the CSS z-index (100002) with a value derived from the live
+  // tool-window stack so the kebab menu stays above its modal even after the
+  // bring-to-front counter climbs past the static value (#4720).
+  menu.style.zIndex = String(topPortalZ());
   const r = btn.getBoundingClientRect();
   menu.style.top = (r.bottom + 4) + 'px';
   menu.style.right = Math.max(6, window.innerWidth - r.right) + 'px';

static/js/tasks.js

@@ -6,6 +6,7 @@ import uiModule from './ui.js';
 import markdownModule from './markdown.js';
 import * as spinnerModule from './spinner.js';
 import { makeWindowDraggable } from './windowDrag.js';
+import { topPortalZ } from './toolWindowZOrder.js';
 import { sortModelIds } from './modelSort.js';
 import { ordinalSuffix } from './util/ordinal.js';
 import { bindMenuDismiss, dismissOrRemove } from './escMenuStack.js';
@@ -903,7 +904,7 @@ function _showTaskDropdown(anchor, items) {
   document.querySelectorAll('.task-dropdown').forEach(dismissOrRemove);
   const dd = document.createElement('div');
   dd.className = 'task-dropdown';
-  dd.style.cssText = 'position:fixed;z-index:100000;background:var(--panel);border:1px solid var(--border);border-radius:6px;box-shadow:0 4px 12px rgba(0,0,0,0.3);padding:4px;min-width:120px;';
+  dd.style.cssText = 'position:fixed;background:var(--panel);border:1px solid var(--border);border-radius:6px;box-shadow:0 4px 12px rgba(0,0,0,0.3);padding:4px;min-width:120px;';
   items.forEach(item => {
     const btn = document.createElement('button');
     btn.style.cssText = 'display:flex;align-items:center;gap:8px;width:100%;text-align:left;padding:6px 10px;border:none;background:none;color:var(--fg);font-size:11px;font-family:inherit;cursor:pointer;border-radius:4px;transition:background 0.1s;';
@@ -919,6 +920,10 @@ function _showTaskDropdown(anchor, items) {
     dd.appendChild(btn);
   });
   document.body.appendChild(dd);
+  // Sit above the currently-raised tool modal at any stack depth (#4720): the
+  // modal bring-to-front counter climbs unbounded, so a hardcoded z eventually
+  // loses. topPortalZ() derives the value from the live tool-window stack.
+  dd.style.zIndex = String(topPortalZ());
   const rect = anchor.getBoundingClientRect();
   let top = rect.bottom + 4;
   let left = rect.right - dd.offsetWidth;

static/style.css

@@ -16960,7 +16960,8 @@ body:not(.email-doc-split-active) #email-lib-modal.email-lib-fullscreen:not(.mod
 /* Kebab dropdown */
 .skill-kebab-menu {
   position: fixed;
-  z-index: 100002;
+  /* z-index is set inline via topPortalZ() at open time (#4720); a static
+     value here loses once the modal bring-to-front counter climbs past it. */
   min-width: 150px;
   padding: 4px;
   background: var(--panel, var(--bg));