fix(ui): robust grid table states — natural row heights, themed pagination, DOM skeleton

Rows expanded unboundedly because `fixedHeader: true` + a fixed `height`
forced a scroll container that filled itself with stretched rows on short
result sets. Pagination text rendered white-on-white because the shared
button base (app-shell.css) redefines `--app-color` as `--app-primary-inverse`
in the button scope, so `color: var(--app-color)` in an override resolves
to white. Sort-column headers looked misaligned because Grid.js uses floats
to place label and sort icon, which ignore the cell's vertical-align.

- Sticky header is now opt-in; default scroll behavior is page-level.
- Row heights come from padding + line-height only (no fixed `height`).
- Pagination buttons theme via `--app-background-color`/`--app-color`
  redefinition (the Pico convention) using `--app-form-element-color`,
  which is not shadowed in the button scope. `margin-inline-start: auto`
  on `.gridjs-pages` guarantees right-alignment even without a summary.
- Sort headers use `inline-block` + `vertical-align: middle` instead of
  vendor floats so label and icon share one cross-axis center.
- Loading UX replaced with a real `<table>` skeleton that mirrors the
  final column count + outer layout (card + footer with summary and
  5 pager placeholders). Grid.js mount point is hidden via
  `.app-grid-shell-loading > :not(.app-grid-skeleton)` — vendor wraps
  its own `.gridjs-container` one level deeper, so a direct-child
  selector on the mount element is required.
- Re-fetch state shows a thin top progress bar + faded tbody (GitHub
  pattern) so existing data stays as context.
- `prefers-reduced-motion` disables all skeleton/progress animations.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

web/js/core/app-grid-factory.js

@@ -135,7 +135,11 @@ export function createServerGrid(options) {
   }
 
   const uiConfig = ui && typeof ui === 'object' ? ui : {};
-  const stickyHeaderEnabled = uiConfig.stickyHeader !== false;
+  // Sticky header is opt-in: enabling it forces a fixed-height scroll container
+  // inside the wrapper (Grid.js requirement for `fixedHeader`). On short result
+  // sets that container fills empty space and makes rows visually expand. The
+  // Stripe-like default scrolls on the page, not in the table.
+  const stickyHeaderEnabled = uiConfig.stickyHeader === true;
   const gridHeight = typeof uiConfig.height === 'string' && uiConfig.height.trim() !== ''
     ? uiConfig.height.trim()
     : DEFAULT_GRID_HEIGHT;
@@ -297,6 +301,7 @@ export function createServerGrid(options) {
       || 'Press Enter to open row'
   ).trim() || 'Press Enter to open row';
   const gridRetryLabel = String(language?.errorRetry || 'Retry').trim() || 'Retry';
+  const gridLoadingLabel = String(language?.loading || 'Loading').trim() || 'Loading';
   const resolveRowOpenUrl = (rowData, rowIndex = -1) => {
     if (!rowInteractionEnabled) {
       return '';
@@ -721,6 +726,106 @@ export function createServerGrid(options) {
     plugins
   });
 
+  // DOM-based skeleton (Stripe/GitHub-style): render a real table with the
+  // same column structure as the final grid, so the transition to real data
+  // is layout-stable and never flickers. We wrap the container in a shell so
+  // the skeleton can live as a sibling — Grid.js' render() controls the
+  // container's subtree and would wipe any skeleton placed inside it.
+  const shellEl = document.createElement('div');
+  shellEl.className = 'app-grid-shell';
+  containerEl.parentNode?.insertBefore(shellEl, containerEl);
+  shellEl.appendChild(containerEl);
+
+  const skeletonEnabled = loadingMode === 'skeleton';
+  const SKELETON_ROW_COUNT = 15;
+  const SKELETON_BAR_WIDTHS = ['72%', '58%', '64%', '44%', '70%', '52%', '60%', '48%'];
+  const SKELETON_PAGINATION_BUTTONS = 5;
+
+  const visibleSkeletonColumns = normalizedColumns.filter((col) => !col?.hidden && !col?.plugin);
+
+  const buildSkeletonBar = (width) => {
+    const bar = document.createElement('span');
+    bar.className = 'app-grid-skeleton-bar';
+    bar.style.width = width;
+    return bar;
+  };
+
+  const buildSkeleton = () => {
+    const root = document.createElement('div');
+    root.className = 'app-grid-skeleton';
+    root.setAttribute('role', 'status');
+    root.setAttribute('aria-label', gridLoadingLabel);
+    root.setAttribute('aria-live', 'polite');
+
+    const srLabel = document.createElement('span');
+    srLabel.className = 'app-grid-skeleton-sr';
+    srLabel.textContent = gridLoadingLabel;
+    root.appendChild(srLabel);
+
+    const table = document.createElement('table');
+    table.className = 'app-grid-skeleton-table';
+    table.setAttribute('aria-hidden', 'true');
+
+    const thead = document.createElement('thead');
+    const headRow = document.createElement('tr');
+    visibleSkeletonColumns.forEach(() => {
+      const th = document.createElement('th');
+      th.className = 'app-grid-skeleton-cell app-grid-skeleton-cell-head';
+      th.appendChild(buildSkeletonBar('55%'));
+      headRow.appendChild(th);
+    });
+    thead.appendChild(headRow);
+    table.appendChild(thead);
+
+    const tbody = document.createElement('tbody');
+    for (let rowIdx = 0; rowIdx < SKELETON_ROW_COUNT; rowIdx += 1) {
+      const tr = document.createElement('tr');
+      tr.className = 'app-grid-skeleton-row';
+      visibleSkeletonColumns.forEach((_col, colIdx) => {
+        const td = document.createElement('td');
+        td.className = 'app-grid-skeleton-cell';
+        const width = SKELETON_BAR_WIDTHS[(rowIdx + colIdx) % SKELETON_BAR_WIDTHS.length];
+        td.appendChild(buildSkeletonBar(width));
+        tr.appendChild(td);
+      });
+      tbody.appendChild(tr);
+    }
+    table.appendChild(tbody);
+    root.appendChild(table);
+
+    // Footer skeleton: mirrors the real pagination layout — summary (results
+    // count) on the left, pagination buttons on the right — so the transition
+    // doesn't shift the surrounding page layout.
+    const footer = document.createElement('div');
+    footer.className = 'app-grid-skeleton-footer';
+    footer.setAttribute('aria-hidden', 'true');
+
+    const summary = document.createElement('div');
+    summary.className = 'app-grid-skeleton-summary';
+    summary.appendChild(buildSkeletonBar('100%'));
+    footer.appendChild(summary);
+
+    const pager = document.createElement('div');
+    pager.className = 'app-grid-skeleton-pager';
+    for (let i = 0; i < SKELETON_PAGINATION_BUTTONS; i += 1) {
+      const btn = document.createElement('span');
+      btn.className = 'app-grid-skeleton-pager-button';
+      pager.appendChild(btn);
+    }
+    footer.appendChild(pager);
+
+    root.appendChild(footer);
+    return root;
+  };
+
+  let skeletonEl = null;
+  if (skeletonEnabled && visibleSkeletonColumns.length > 0) {
+    skeletonEl = buildSkeleton();
+    shellEl.insertBefore(skeletonEl, containerEl);
+    shellEl.classList.add('app-grid-shell-loading');
+    containerEl.setAttribute('aria-busy', 'true');
+  }
+
   grid.render(containerEl);
   setTimeout(() => {
     initSelectAll();
@@ -732,6 +837,12 @@ export function createServerGrid(options) {
     if (hasLoadedOnce) {return;}
     hasLoadedOnce = true;
     containerEl.classList.add('gridjs-has-loaded');
+    containerEl.removeAttribute('aria-busy');
+    shellEl.classList.remove('app-grid-shell-loading');
+    if (skeletonEl) {
+      skeletonEl.remove();
+      skeletonEl = null;
+    }
   };
   const setUpdating = () => containerEl.classList.add('gridjs-is-updating');
   const clearUpdating = () => containerEl.classList.remove('gridjs-is-updating');