feat(ui): replace heatmap with category breakdown + skeletons

Remove dead HeatmapWidget and the category heatmap grid. Replace with an
"Emails by Category" ranked horizontal bar list (top 8), each bar a
clickable button routing to the category folder via CAT_SLUG. Add Skeleton
loading placeholders and richer EmptyState fallbacks to dashboard widgets.
Drop the unused AnalyticsApi.heatmap client method and dead heatmap CSS.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/api/client.js

@@ -38,7 +38,6 @@ export const AnalyticsApi = {
   health: () => api.get('/analytics/health').then((r) => r.data),
   topSenders: (take = 20) => api.get(`/analytics/top-senders?take=${take}`).then((r) => r.data),
   volume: (days = 90) => api.get(`/analytics/volume?days=${days}`).then((r) => r.data),
-  heatmap: () => api.get('/analytics/heatmap').then((r) => r.data),
   categoryHeatmap: () => api.get('/analytics/category-heatmap').then((r) => r.data),
   attachments: () => api.get('/analytics/attachments').then((r) => r.data),
   sidebarCounts: () => api.get('/analytics/sidebar-counts').then((r) => r.data),

frontend/src/components/widgets.jsx

@@ -1,13 +1,16 @@
 import { useEffect, useState } from 'react';
 import { useNavigate } from 'react-router-dom';
-import { Bar, Line, Doughnut } from 'react-chartjs-2';
+import { Line, Doughnut } from 'react-chartjs-2';
+import { Inbox } from 'lucide-react';
 import { AnalyticsApi } from '../api/client.js';
+import { Skeleton } from './ui/skeleton.jsx';
+import { EmptyState } from './ui/misc.jsx';
 import {
-  Chart as ChartJS, CategoryScale, LinearScale, BarElement, PointElement,
+  Chart as ChartJS, CategoryScale, LinearScale, PointElement,
   LineElement, ArcElement, Tooltip, Legend
 } from 'chart.js';
 
-ChartJS.register(CategoryScale, LinearScale, BarElement, PointElement, LineElement, ArcElement, Tooltip, Legend);
+ChartJS.register(CategoryScale, LinearScale, PointElement, LineElement, ArcElement, Tooltip, Legend);
 
 const fmtBytes = (b) => {
   if (!b) return '0 B';
@@ -77,32 +80,6 @@ export function VolumeWidget({ volume }) {
   );
 }
 
-export function HeatmapWidget({ heatmap }) {
-  if (!heatmap) return <Empty />;
-  const days = ['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat'];
-  const max = Math.max(1, ...heatmap.map((c) => c.count));
-  const grid = {};
-  heatmap.forEach((c) => { grid[`${c.dayOfWeek}-${c.hour}`] = c.count; });
-  return (
-    <div className="widget">
-      <h3>Activity Heatmap</h3>
-      <div className="heatmap">
-        {days.map((d, dow) => (
-          <div className="hm-row" key={dow}>
-            <span className="hm-day">{d}</span>
-            {Array.from({ length: 24 }, (_, h) => {
-              const v = grid[`${dow}-${h}`] || 0;
-              return <span key={h} className="hm-cell" style={{ opacity: 0.1 + 0.9 * (v / max) }} title={`${d} ${h}:00 — ${v}`} />;
-            })}
-          </div>
-        ))}
-      </div>
-    </div>
-  );
-}
-
-const DOW = ['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat'];
-
 // Maps EmailCategory enum name → folder slug or search query
 const CAT_SLUG = {
   Finance:          '/app/folder/finance',
@@ -135,41 +112,64 @@ const CAT_SLUG = {
   Unknown:          '/app/folder/allmail',
 };
 
-export function CategoryHeatmapWidget() {
+// "Emails by Category" — ranked horizontal bar list. Aggregates the
+// category×day-of-week cells into per-category totals; each bar links to
+// that category's folder via CAT_SLUG.
+export function CategoryBreakdownWidget() {
   const [cells, setCells] = useState(null);
   const navigate = useNavigate();
   useEffect(() => { AnalyticsApi.categoryHeatmap().then(setCells).catch(() => setCells([])); }, []);
 
-  if (!cells) return <div className="widget"><div className="muted">Loading…</div></div>;
+  if (!cells) {
-  if (cells.length === 0) return <div className="widget"><h3>Category Heatmap</h3><div className="muted">No data yet — run a sync.</div></div>;
+    return (
+      <div className="widget">
+        <h3>Emails by Category</h3>
+        <div className="cat-bars">
+          {Array.from({ length: 6 }, (_, i) => <Skeleton key={i} className="h-6 w-full" />)}
+        </div>
+      </div>
+    );
+  }
 
-  const categories = [...new Set(cells.map((c) => c.category))].sort();
+  const totals = {};
-  const max = Math.max(1, ...cells.map((c) => c.count));
+  cells.forEach((c) => { totals[c.category] = (totals[c.category] || 0) + c.count; });
-  const grid = {};
+  const ranked = Object.entries(totals)
-  cells.forEach((c) => { grid[`${c.category}-${c.dayOfWeek}`] = c.count; });
+    .map(([category, count]) => ({ category, count }))
+    .sort((a, b) => b.count - a.count)
+    .slice(0, 8);
+
+  if (ranked.length === 0) {
+    return (
+      <div className="widget">
+        <h3>Emails by Category</h3>
+        <EmptyState icon={Inbox} title="No data yet — run a sync" description="Category totals appear once your inbox has been synced." />
+      </div>
+    );
+  }
+
+  const max = Math.max(1, ...ranked.map((r) => r.count));
 
   return (
     <div className="widget">
-      <h3>Category Heatmap</h3>
+      <h3>Emails by Category</h3>
-      <div className="cat-heatmap">
+      <div className="cat-bars">
-        <div className="chm-row chm-head">
+        {ranked.map(({ category, count }) => {
-          <span className="chm-label" />
+          const dest = CAT_SLUG[category];
-          {DOW.map((d) => <span key={d} className="chm-col">{d}</span>)}
-        </div>
-        {categories.map((cat) => {
-          const dest = CAT_SLUG[cat];
           return (
-            <div className="chm-row" key={cat}>
+            <button
-              <span
+              type="button"
-                className={`chm-label${dest ? ' chm-label--link' : ''}`}
+              className={`cat-bar${dest ? ' cat-bar--link' : ''}`}
-                title={dest ? `View ${cat} emails` : cat}
+              key={category}
-                onClick={dest ? () => navigate(dest) : undefined}
+              disabled={!dest}
-              >{cat}</span>
+              title={dest ? `View ${category} emails` : category}
-              {DOW.map((_, dow) => {
+              onClick={dest ? () => navigate(dest) : undefined}
-                const v = grid[`${cat}-${dow}`] || 0;
+            >
-                return <span key={dow} className="chm-cell" style={{ opacity: 0.12 + 0.88 * (v / max) }} title={`${cat} · ${DOW[dow]} — ${v}`}>{v || ''}</span>;
+              <span className="cat-bar-label">{category}</span>
-              })}
+              <span className="cat-bar-track">
-            </div>
+                <span className="cat-bar-fill" style={{ width: `${(count / max) * 100}%` }} />
+              </span>
+              <span className="cat-bar-count">{count.toLocaleString()}</span>
+            </button>
           );
         })}
       </div>
@@ -196,4 +196,10 @@ export function StorageWidget({ bytes }) {
   return <StatCard label="Estimated Storage" value={fmtBytes(bytes)} />;
 }
 
-function Empty() { return <div className="widget"><div className="muted">No data yet — run a sync.</div></div>; }
+function Empty() {
+  return (
+    <div className="widget">
+      <EmptyState icon={Inbox} title="No data yet — run a sync" description="This widget populates after your inbox has been synced." />
+    </div>
+  );
+}

frontend/src/pages/Dashboard.jsx

@@ -6,8 +6,9 @@ import { AnalyticsApi, LayoutApi, ExportApi, SyncApi } from '../api/client.js';
 import SyncSplash from '../components/SyncSplash.jsx';
 import {
   HealthWidget, StatCard, TopSendersWidget, VolumeWidget,
-  CategoryHeatmapWidget, AttachmentsWidget, StorageWidget
+  CategoryBreakdownWidget, AttachmentsWidget, StorageWidget
 } from '../components/widgets.jsx';
+import { Skeleton } from '../components/ui/skeleton.jsx';
 
 // Default grid geometry; overridden by the user's saved layout.
 const DEFAULT_LAYOUT = [
@@ -17,12 +18,23 @@ const DEFAULT_LAYOUT = [
   { i: 'storage', x: 7, y: 0, w: 2, h: 2 },
   { i: 'top-senders', x: 3, y: 2, w: 3, h: 5 },
   { i: 'volume', x: 6, y: 2, w: 6, h: 4 },
-  { i: 'category-heatmap', x: 0, y: 5, w: 6, h: 5 },
+  { i: 'category-breakdown', x: 0, y: 5, w: 6, h: 5 },
   { i: 'attachments', x: 6, y: 6, w: 4, h: 4 },
 ];
 
 const ALL_WIDGETS = DEFAULT_LAYOUT.map((l) => l.i);
 
+function WidgetSkeleton() {
+  return (
+    <div className="widget">
+      <Skeleton className="mb-3 h-4 w-1/3" />
+      <Skeleton className="mb-2 h-3 w-full" />
+      <Skeleton className="mb-2 h-3 w-5/6" />
+      <Skeleton className="h-3 w-2/3" />
+    </div>
+  );
+}
+
 export default function Dashboard() {
   const [data, setData] = useState(null);
   const [layout, setLayout] = useState(DEFAULT_LAYOUT);
@@ -87,15 +99,18 @@ export default function Dashboard() {
   const visibleLayout = useMemo(() => layout.filter((l) => !hidden.includes(l.i)), [layout, hidden]);
 
   const render = (key) => {
+    // category-breakdown self-fetches, so it renders regardless of dashboard load state.
+    if (key === 'category-breakdown') return <CategoryBreakdownWidget />;
+    // While the dashboard payload loads, show a skeleton placeholder per widget.
+    if (!data) return <WidgetSkeleton />;
     switch (key) {
-      case 'inbox-health': return <HealthWidget health={data?.health} />;
+      case 'inbox-health': return <HealthWidget health={data.health} />;
-      case 'total-emails': return <StatCard label="Total Emails" value={(data?.totalEmails ?? 0).toLocaleString()} to="/app/folder/allmail" />;
+      case 'total-emails': return <StatCard label="Total Emails" value={(data.totalEmails ?? 0).toLocaleString()} to="/app/folder/allmail" />;
-      case 'unread-emails': return <StatCard label="Unread" value={(data?.unreadEmails ?? 0).toLocaleString()} to="/app/folder/unread" />;
+      case 'unread-emails': return <StatCard label="Unread" value={(data.unreadEmails ?? 0).toLocaleString()} to="/app/folder/unread" />;
-      case 'storage': return <StorageWidget bytes={data?.storageEstimateBytes} />;
+      case 'storage': return <StorageWidget bytes={data.storageEstimateBytes} />;
-      case 'top-senders': return <TopSendersWidget senders={data?.topSenders} />;
+      case 'top-senders': return <TopSendersWidget senders={data.topSenders} />;
-      case 'volume': return <VolumeWidget volume={data?.volumeOverTime} />;
+      case 'volume': return <VolumeWidget volume={data.volumeOverTime} />;
-      case 'category-heatmap': return <CategoryHeatmapWidget />;
+      case 'attachments': return <AttachmentsWidget attachments={data.attachmentBreakdown} />;
-      case 'attachments': return <AttachmentsWidget attachments={data?.attachmentBreakdown} />;
       default: return null;
     }
   };

frontend/src/styles.css

@@ -115,8 +115,6 @@ button:disabled { opacity: 0.5; cursor: default; }
 .widget--link:hover { border-color: var(--accent); }
 .mini-row--link { cursor: pointer; }
 .mini-row--link:hover td { color: var(--accent); }
-.chm-label--link { cursor: pointer; text-decoration: underline dotted; }
-.chm-label--link:hover { color: var(--accent); }
 .widget canvas { flex: 1; min-height: 0; }
 
 .stat { align-items: flex-start; justify-content: center; }
@@ -135,17 +133,21 @@ table.grid th, table.grid td { padding: 8px; border-bottom: 1px solid #2c3550; t
 .num { text-align: right; }
 .muted { color: var(--muted); font-size: 12px; }
 
-.heatmap { display: flex; flex-direction: column; gap: 2px; }
+/* Emails by Category — ranked horizontal bars */
-.hm-row { display: flex; align-items: center; gap: 2px; }
+.cat-bars { display: flex; flex-direction: column; gap: 6px; overflow: auto; }
-.hm-day { width: 30px; font-size: 10px; color: var(--muted); }
+.cat-bar {
-.hm-cell { width: 10px; height: 10px; background: var(--accent); border-radius: 2px; }
+  display: grid; grid-template-columns: 92px 1fr 40px; gap: 8px; align-items: center;
-
+  width: 100%; padding: 3px 4px; margin: 0; border: none; background: transparent;
-/* Category heatmap */
+  border-radius: 6px; text-align: left; font: inherit; color: inherit;
-.cat-heatmap { display: flex; flex-direction: column; gap: 3px; overflow: auto; }
+}
-.chm-row { display: grid; grid-template-columns: 92px repeat(7, 1fr); gap: 3px; align-items: stretch; }
+.cat-bar--link { cursor: pointer; }
-.chm-head .chm-col { font-size: 10px; color: var(--muted); text-align: center; }
+.cat-bar--link:hover { background: rgba(255, 255, 255, 0.04); }
-.chm-label { font-size: 11px; color: var(--muted); overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
+.cat-bar:disabled { cursor: default; }
-.chm-cell { background: var(--accent); border-radius: 3px; min-height: 22px; display: flex; align-items: center; justify-content: center; font-size: 10px; color: #fff; }
+.cat-bar-label { font-size: 11px; color: var(--muted); overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
+.cat-bar-track { height: 14px; background: rgba(255, 255, 255, 0.06); border-radius: 4px; overflow: hidden; }
+.cat-bar-fill { display: block; height: 100%; background: var(--accent); border-radius: 4px; min-width: 2px; }
+.cat-bar-count { font-size: 11px; color: var(--muted); text-align: right; font-variant-numeric: tabular-nums; }
+.cat-bar--link:hover .cat-bar-label { color: var(--accent); }
 
 /* react-grid-layout resize handle — make it clearly visible on the dark theme */
 .react-resizable-handle {