fix: phone overlay, district modal z-index — 40/40 browser tests pass

Root causes found via Playwright + CSS rule inspection:
- Phone overlay: cosysim-phone-panel.css sets display:none, requires
  .open class (not aria-hidden). Added .open toggle to open/close.
- District modal: z-index was 100 (below navbar at 9100). Raised to 9500.
- Phone overlay z-index: was var(--cs-z-phone, 200). Raised to 9000.

All verified with Playwright browser test suite: 40/40 passing.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: nihilistau

content/scenes/neoncity/static/neoncity.css

@@ -867,7 +867,7 @@ html, body {
 .district-modal {
     position: fixed;
     inset: 0;
-    z-index: 100;
+    z-index: 9500;  /* v1.43.0 — above navbar (9100) and all overlays */
     display: flex;
     align-items: center;
     justify-content: center;

content/shared/static/css/cosysim-neon-hud.css

@@ -1261,7 +1261,7 @@
   width: 375px;
   height: calc(100vh - var(--cs-navbar-height, 48px) - 32px - 32px);
   max-height: 780px;
-  z-index: var(--cs-z-phone, 200);
+  z-index: 9000;
 
   border-radius: 16px;
   overflow: hidden;

content/shared/static/js/cosysim-neon-hud.js

@@ -594,6 +594,7 @@
       }
       if (overlay) {
         overlay.setAttribute('aria-hidden', 'false');
+        overlay.classList.add('open');  // v1.43.0 — phone-panel.css uses .open class
         overlay.classList.toggle('cs-phone-overlay--edge', !this._rightOpen);
       }
       if (phoneDot) phoneDot.classList.add('cs-hud__phone-dot--active');
@@ -606,7 +607,10 @@
       const phoneDot = document.querySelector('.cs-hud__phone-dot');
       const btn      = document.getElementById('hud-toggle-phone');
       // Hide overlay but keep iframe loaded to preserve phone state + badge
-      if (overlay) overlay.setAttribute('aria-hidden', 'true');
+      if (overlay) {
+        overlay.setAttribute('aria-hidden', 'true');
+        overlay.classList.remove('open');  // v1.43.0 — phone-panel.css .open class
+      }
       if (phoneDot) phoneDot.classList.remove('cs-hud__phone-dot--active');
       if (btn) btn.classList.remove('cs-hud__toggle--active');
     }