Sticky status headers; fix floating details-view button on phones

- Status group headers ("Not Started (37)") stick under the top nav while
  scrolling through their group, on every screen size
- On desktop the column header and filter rows stick beneath the group
  header (table wrappers no longer clip them; these fixed-layout tables
  never scroll sideways at desktop widths)
- layout.js measures the nav, group header and header row heights so the
  sticky rows stack without gaps, re-measuring on re-render/resize/scroll
- Phones: the Advanced/Simple View button sits on its own line under the
  device name instead of floating over the dialog content
- Rename mobile.css/js to layout.css/js now that they hold desktop rules

web/index.html

@@ -351,8 +351,8 @@
             .status-btn:hover { color: white; background: rgba(255,255,255,0.1); }
         }
     </style>
-    <link rel="stylesheet" href="/mobile.css">
-    <script src="/mobile.js"></script>
+    <link rel="stylesheet" href="/layout.css">
+    <script src="/layout.js"></script>
 </head>
 <body>
 

web/layout.css

@@ -1,9 +1,36 @@
 /*
- * Small-screen layout for the dashboard (phones, tablets, narrow windows).
- * Loaded after the page's own <style> block. Desktop layouts are untouched: every rule
- * here is inside a max-width media query.
+ * Layout additions for the dashboard, loaded after the page's own <style> block:
+ *   - sticky status-group headers (all sizes) and sticky column headers (desktop)
+ *   - card view for tables on phones and tablets
+ *   - small-screen fixes for forms, docs and dialogs
+ * layout.js measures the sticky offsets and labels card cells.
  */
 
+/* ---------------------------------------------------------------------------------------
+ *  Sticky headers
+ *
+ *  A status group's header ("Not Started (37)") sticks under the top nav while you scroll
+ *  through that group, then hands over to the next group's header. On desktop the column
+ *  header and filter rows stick beneath it. layout.js sets --nav-h (top nav height) and,
+ *  per table, --sticky-top (nav + group header) and --thead-r1 (header row height).
+ * ------------------------------------------------------------------------------------- */
+.group-header { position: sticky; top: var(--nav-h, 60px); z-index: 30; }
+
+@media (min-width: 1101px) {
+    /* An overflowing wrapper would capture the sticky rows; these tables never need to
+       scroll sideways at desktop widths (they're fixed-layout, 100% wide) */
+    #masterList .table-wrapper, #software .table-wrapper, .stack-box.table-wrapper { overflow: visible !important; }
+
+    .master-table:not(#table-custom) thead th {
+        position: sticky; top: var(--sticky-top, 112px); z-index: 20;
+    }
+    .master-table:not(#table-custom) thead tr.filter-row th {
+        top: calc(var(--sticky-top, 112px) + var(--thead-r1, 38px) - 2px); z-index: 19;   /* -2px: no seam from collapsed borders */
+        /* the original header tint, but opaque so rows don't show through */
+        background: linear-gradient(rgba(0,0,0,0.2), rgba(0,0,0,0.2)), var(--bg-card);
+    }
+}
+
 /* ---------------------------------------------------------------------------------------
  *  Card view for data tables (phones and tablets)
  *
@@ -149,6 +176,10 @@
     .modal-header { padding: 14px 14px 8px; }
     .modal-header h2 { font-size: 1.2em; word-break: break-all; }
 
+    /* Details title: the Advanced/Simple View button gets its own line under the device
+       name instead of floating over the content */
+    #detailsTitle button { float: none !important; display: block; margin: 10px 0 0 !important; font-size: 0.65em !important; }
+
     /* Device details: Advanced View's source / overview / destination columns stack,
        and the whole dialog scrolls instead of each column scrolling separately */
     #detailsModal .modal-content { height: auto !important; overflow-y: auto !important; display: block !important; }

web/layout.js

@@ -1,11 +1,15 @@
 /*
- * Card layout support for small screens.
+ * Layout helpers (see layout.css).
  *
- * On phones and tablets (see mobile.css) each table row is shown as a card, with every
- * cell rendered as "Column name: value". CSS can't look up a cell's column header, so
- * this copies each header's text onto its cells as data-label. The dashboard re-renders
- * its tables constantly, so labels are reapplied (once per frame at most) whenever the
- * DOM changes. On wide screens it does nothing.
+ * Sticky headers: measures the top nav and each table's group header so the column
+ * header rows can stick directly beneath them (--nav-h, --sticky-top, --thead-r1).
+ *
+ * Card view: on phones and tablets each table row is shown as a card, with every cell
+ * rendered as "Column name: value". CSS can't look up a cell's column header, so this
+ * copies each header's text onto its cells as data-label.
+ *
+ * The dashboard re-renders its tables constantly, so both are reapplied (once per frame
+ * at most) whenever the DOM changes.
  */
 (function () {
     'use strict';
@@ -70,9 +74,36 @@
         if (btn.innerHTML !== html) btn.innerHTML = html;
     }
 
+    // --- Sticky offsets ---------------------------------------------------------------
+    function setVar(el, name, value) {
+        if (el.style.getPropertyValue(name) !== value) el.style.setProperty(name, value);
+    }
+    function groupHeaderFor(table) {
+        // The group header is a sibling of the table or of its wrapper
+        for (let el = table.parentElement, depth = 0; el && depth < 3; el = el.parentElement, depth++) {
+            const gh = el.querySelector(':scope > .group-header');
+            if (gh) return gh;
+        }
+        return null;
+    }
+    function updateSticky() {
+        const nav = document.querySelector('.top-nav');
+        const navH = nav ? nav.offsetHeight : 60;
+        setVar(document.documentElement, '--nav-h', navH + 'px');
+        document.querySelectorAll('table.master-table').forEach(table => {
+            const gh = groupHeaderFor(table);
+            const ghH = gh ? gh.offsetHeight : 0;
+            const firstRow = table.tHead && table.tHead.rows[0];
+            if (!firstRow || !firstRow.offsetHeight) return;   // hidden page/group: keep old values
+            setVar(table, '--sticky-top', (navH + ghH) + 'px');
+            setVar(table, '--thead-r1', firstRow.offsetHeight + 'px');
+        });
+    }
+
     let queued = false;
     function run() {
         queued = false;
+        updateSticky();
         if (!cardsQuery.matches) return;
         document.querySelectorAll('table.master-table').forEach(labelTable);
     }
@@ -86,6 +117,10 @@
         new MutationObserver(schedule).observe(document.body, { childList: true, subtree: true });
         if (cardsQuery.addEventListener) cardsQuery.addEventListener('change', schedule);
         else cardsQuery.addListener(schedule);
+        window.addEventListener('resize', schedule);
+        // Groups and pages are shown by toggling display (not a DOM change), so also
+        // re-measure as the user scrolls; writes only happen when a value changes.
+        window.addEventListener('scroll', schedule, { passive: true });
         schedule();
     }
     if (document.readyState === 'loading') document.addEventListener('DOMContentLoaded', start);