Default the initial hour to local time of day instead of always Prime

Visiting the app with no hour in the URL previously always showed
Prime for today, since selectedHour was hardcoded in AppState. Now it
picks the hour whose band contains the visitor's local clock time.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01L3wxvz3mPXiHxkPB5JpnmD

src/app-state.ts

@@ -16,9 +16,22 @@ export function todayIso(): string {
   return `${yyyy}-${mm}-${dd}`;
 }
 
+/** Which hour to default to when the URL doesn't specify one, based on local wall-clock time. */
+export function defaultHourForTime(date: Date): HourId {
+  const h = date.getHours();
+  if (h < 6) return 'matins';
+  if (h < 8) return 'lauds';
+  if (h < 9) return 'prime';
+  if (h < 12) return 'terce';
+  if (h < 15) return 'sext';
+  if (h < 17) return 'none';
+  if (h < 21) return 'vespers';
+  return 'compline';
+}
+
 const state: AppState = {
   date: todayIso(),
-  selectedHour: 'prime',
+  selectedHour: defaultHourForTime(new Date()),
   languages: ['en'],
 };