Card layout for tables on phones and tablets; fit terminal bar

Sideways-scrolling tables only showed a few of the 11 columns at a time on
a phone or iPad. Below 1100px (where the nav already collapses) each row
now renders as a card: the device as the title and every other column as
a labelled line, one card per row on phones and two or more on tablets.

- web/mobile.js copies column names onto cells (data-label) for the cards
  and re-applies them as the dashboard re-renders; no-op on wide screens
- Column filters fold behind a "Show filters" button with an active count
- Custom View keeps its sort/filter header as a strip of chips
- Terminal: Follow and the "your actions (simulated)" legend move into the
  terminal window's title bar; tabs read "Server" / "Worker" on phones, so
  LIVE, the legend and Follow are all visible on small screens

web/mobile.js

@@ -0,0 +1,93 @@
+/*
+ * Card layout support for small screens.
+ *
+ * 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.
+ */
+(function () {
+    'use strict';
+
+    const cardsQuery = window.matchMedia('(max-width: 1100px)');
+    const clean = text => text.replace(/[\u2195\u25B2\u25BC\u00D7\u2715]/g, '').replace(/\s+/g, ' ').trim();
+
+    function labelTable(table) {
+        const thead = table.tHead;
+        if (!thead) return;
+
+        // The header row is the one with the most text (Custom View has a drag-handle row above it)
+        let headerRow = null, best = -1;
+        for (const row of thead.rows) {
+            if (row.classList.contains('filter-row')) continue;
+            const named = Array.from(row.cells).filter(c => clean(c.textContent)).length;
+            if (named > best) { best = named; headerRow = row; }
+        }
+        if (!headerRow) return;
+
+        for (const row of thead.rows) {
+            if (row === headerRow) row.classList.add('card-label-row');
+            else if (!row.classList.contains('filter-row')) row.classList.add('card-aux-row');
+        }
+
+        const labels = Array.from(headerRow.cells).map(c => clean(c.textContent));
+        const apply = row => {
+            Array.from(row.cells).forEach((cell, i) => {
+                const label = cell.colSpan > 1 ? '' : (labels[i] || '');
+                if (cell.dataset.label !== label) cell.dataset.label = label;
+            });
+        };
+        thead.querySelectorAll('tr.filter-row').forEach(apply);
+        for (const body of table.tBodies) for (const row of body.rows) apply(row);
+
+        addFilterToggle(table, thead.querySelector('tr.filter-row'));
+    }
+
+    // Column filters take a lot of room above every card group, so they fold behind a
+    // button that also shows how many filters are active.
+    function addFilterToggle(table, filterRow) {
+        if (!filterRow) return;
+        let btn = table.previousElementSibling;
+        if (!btn || !btn.classList.contains('card-filter-toggle')) {
+            btn = document.createElement('button');
+            btn.type = 'button';
+            btn.className = 'card-filter-toggle';
+            btn.addEventListener('click', () => { table.classList.toggle('show-filters'); updateToggle(table, btn); });
+            table.parentNode.insertBefore(btn, table);
+            filterRow.addEventListener('input', () => updateToggle(table, btn));
+            filterRow.addEventListener('change', () => updateToggle(table, btn));
+        }
+        updateToggle(table, btn);
+    }
+    function updateToggle(table, btn) {
+        const row = table.tHead && table.tHead.querySelector('tr.filter-row');
+        if (!row) return;
+        const active = Array.from(row.querySelectorAll('input[type="text"]')).filter(i => i.value.trim()).length
+                     + row.querySelectorAll('input[type="checkbox"]:checked').length;
+        const open = table.classList.contains('show-filters');
+        const html = `${open ? 'Hide' : 'Show'} filters${active ? ` <span class="count">${active}</span>` : ''}`;
+        if (btn.innerHTML !== html) btn.innerHTML = html;
+    }
+
+    let queued = false;
+    function run() {
+        queued = false;
+        if (!cardsQuery.matches) return;
+        document.querySelectorAll('table.master-table').forEach(labelTable);
+    }
+    function schedule() {
+        if (queued) return;
+        queued = true;
+        requestAnimationFrame(run);
+    }
+
+    function start() {
+        new MutationObserver(schedule).observe(document.body, { childList: true, subtree: true });
+        if (cardsQuery.addEventListener) cardsQuery.addEventListener('change', schedule);
+        else cardsQuery.addListener(schedule);
+        schedule();
+    }
+    if (document.readyState === 'loading') document.addEventListener('DOMContentLoaded', start);
+    else start();
+})();