docs(readme,preview): screenshots of both tabs, a calendar scene on the busiest month

preview/entry.ts

@@ -105,6 +105,17 @@ async function main(): Promise<void> {
     }
     if (scene === "rail-none") store.filterNone();
   }
+  // The month grid on its own, opened on the month the fixtures are busiest in.
+  if (scene === "cal") {
+    const months = new Map<string, number>();
+    for (const item of store.visible) {
+      const key = (item.due ?? item.scheduled)?.slice(0, 7);
+      if (key) months.set(key, (months.get(key) ?? 0) + 1);
+    }
+    const busiest = [...months.entries()].sort((a, b) => b[1] - a[1])[0]?.[0];
+    store.view = "calendar";
+    if (busiest) store.focusDay(`${busiest}-15`);
+  }
   if (scene.startsWith("peek")) {
     if (scene === "peek-cal") store.view = "calendar";
     if (scene === "peek-notes") store.showDone = true;