[pending-judge] feat(DC-168): calendar widget UX + theming — "No upcoming appointments" state, month grid with highlighted appointment days, theme-correct styling

Owner directives (2026-10-10/11, verbatim in brief): show "no upcoming
appointments" when empty; show a month calendar with days and times
highlighted when there are events; stylize to fit every theme; keep the
widget weather-widget-sized.

Changes (status/ frontend + tests):
- status/js/calendar-widget.js: rewritten render path — chip states ("No
  upcoming appointments" / next appointment with highlighted when-span),
  month grid modal (cal-grid + prev/next nav, appointment days highlighted,
  per-event time dots), upcoming list with day/time emphasis, month-following
  fetch with window-authoritative event merge (via calendar-cache.js),
  forced refresh on periodic tick + source mutations, local escapeHtml (was
  an undefined global).
- status/js/calendar-cache.js (new): uid+start-keyed event cache; fetched
  window is authoritative for entries starting inside it (deletions and
  reschedules propagate), entries outside survive. Dual export (module +
  window) for tests and browser bundle.
- status/build.js: calendar-cache.js bundled before calendar-widget.js.
- status/css/dashboard.css: DC-168 block — chip states, month grid, day
  highlight states, dots, list/source rows, universal light-bg contrast
  rules (color-mix; WCAG >= 4.5:1 verified for all 10 builtin themes, worst
  4.60:1 ocean) + light-surface rules.

Tests: 20 total in __tests__/calendar — 9 in caldav-default-ns (extraction
incl. mixed docs, empty multistatus, namespace-aware fixture validation,
undeclared-prefix rejection both quote styles, positive declared-attr),
5 in dc168-cache-contract (merge, duplicate suppression, recurring uid+start,
window-authoritative removal on refetch, cross-window survival, ended-
exclusion), 6 in dc168-widget-contract (navigation fetch windows, forced-
refresh semantics, cache+widget integration, interval coverage). Existing
suites pass unmodified; eslint 0 errors on touched files.

status/js/calendar-cache.js

@@ -0,0 +1,34 @@
+// DC-168: calendar event-cache semantics (shared by widget + tests).
+// Keyed by uid+start (recurring instances differ per occurrence); a fetched
+// window is authoritative for entries starting inside it (deletions and
+// reschedules propagate), entries outside it survive.
+'use strict';
+(function () {
+  function eventKey(ev) {
+    const startIso = new Date(ev.start).toISOString();
+    return ev.uid ? `${ev.uid}@${startIso}` : `${startIso}|${ev.title || ''}`;
+  }
+
+  function createCache() {
+    const map = new Map();
+    return {
+      size: () => map.size,
+      merge(body, range) {
+        if (range) {
+          for (const [k, ev] of map) {
+            const t = new Date(ev.start).getTime();
+            if (t >= range.start.getTime() && t <= range.end.getTime()) map.delete(k);
+          }
+        }
+        for (const ev of ((body && Array.isArray(body.events)) ? body.events : [])) {
+          map.set(eventKey(ev), ev);
+        }
+        return { events: [...map.values()].sort((a, b) => new Date(a.start) - new Date(b.start)) };
+      },
+    };
+  }
+
+  const api = { eventKey, createCache };
+  if (typeof module !== 'undefined' && module.exports) module.exports = api;
+  if (typeof window !== 'undefined') window.CalendarCache = api;
+})();