Color layer headings with their layer color by default

- Research map layer h4 and XL-Stack band h4 now always use the layer
  color (previously dark, only colored when a paper was selected);
  weight stays 900
- Bump CSS/JS cache-busting version so the change reaches cached browsers

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: xinliulab

css/homepage.css

@@ -544,7 +544,7 @@ a {
 .research-map-layer h4 {
   margin: 0;
   padding: 10px 8px 3px;
-  color: var(--accent-deep);
+  color: var(--layer-color);
   font-family: "Merriweather", serif;
   font-size: 0.82rem;
   font-weight: 900;
@@ -919,7 +919,7 @@ a {
 
 .xl-stack-band > h4 {
   margin: 0 0 11px;
-  color: var(--accent-deep);
+  color: var(--stack-color);
   font-family: "Merriweather", serif;
   font-size: 1.12rem;
   font-weight: 900;

index.html

@@ -20,7 +20,7 @@
   <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
   <link href="https://fonts.googleapis.com/css2?family=Merriweather:wght@700&family=Source+Sans+3:wght@400;500;600;700&display=swap" rel="stylesheet">
   <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.0/css/bootstrap.min.css">
-  <link rel="stylesheet" href="css/homepage.css?v=20260917-axis-dot-tight">
+  <link rel="stylesheet" href="css/homepage.css?v=20260917-layer-heading-color">
 </head>
 <body>
   <div class="site-shell">
@@ -436,7 +436,7 @@ <h3 id="citation-modal-title">Citation</h3>
 
   <script src="https://code.jquery.com/jquery-3.5.1.slim.min.js"></script>
   <script src="https://stackpath.bootstrapcdn.com/bootstrap/4.5.0/js/bootstrap.bundle.min.js"></script>
-  <script src="js/homepage.js?v=20260917-axis-dot-tight"></script>
+  <script src="js/homepage.js?v=20260917-layer-heading-color"></script>
   <div style="display: none;" aria-hidden="true">
     <script type="text/javascript" id="mapmyvisitors" src="https://mapmyvisitors.com/map.js?d=RX6JZVxpvzyAHlsWxTEyKE_hWPQXmGtbEacN4FuhKgY&cl=ffffff&w=a"></script>
   </div>

lab.html

@@ -9,7 +9,7 @@
   <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
   <link href="https://fonts.googleapis.com/css2?family=Merriweather:wght@700&family=Source+Sans+3:wght@400;500;600;700&display=swap" rel="stylesheet">
   <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.0/css/bootstrap.min.css">
-  <link rel="stylesheet" href="css/homepage.css?v=20260620-news-scroll">
+  <link rel="stylesheet" href="css/homepage.css?v=20260917-layer-heading-color">
   <link rel="stylesheet" href="css/lab.css?v=20260804-people-links">
 </head>
 <body class="lab-page">