fix(a11y): set crisis overlay initial focus to Call 988 link (#69)

The overlay's showOverlay() called overlayDismissBtn.focus() after
setting overlayDismissBtn.disabled = true. Disabled buttons are not
valid focus targets per WCAG 2.4.3, so keyboard/AT users lost context
at the most critical point.

Fix: focus the Call 988 tel: link (first actionable, non-disabled
element) instead of the disabled dismiss button.

Changes:
- Add overlayCallLink variable from .overlay-call selector
- Focus overlayCallLink instead of overlayDismissBtn in showOverlay()
- Guard with null check for robustness

Closes #69

index.html

@@ -808,6 +808,7 @@ Sovereignty and service always.`;
   var crisisPanel = document.getElementById('crisis-panel');
   var crisisOverlay = document.getElementById('crisis-overlay');
   var overlayDismissBtn = document.getElementById('overlay-dismiss-btn');
+  var overlayCallLink = document.querySelector('#crisis-overlay .overlay-call');
   var statusDot = document.querySelector('.status-dot');
   var statusText = document.getElementById('status-text');
   
@@ -1002,7 +1003,11 @@ Sovereignty and service always.`;
       }
     }, 1000);
 
-    overlayDismissBtn.focus();
+    // Focus the Call 988 link — the first actionable (non-disabled) element.
+    // Disabled buttons are not valid focus targets (WCAG 2.4.3).
+    if (overlayCallLink) {
+      overlayCallLink.focus();
+    }
   }
 
   overlayDismissBtn.addEventListener('click', function() {