Calendar: expose time of day (hour/minute)

Add Hour, Minute and MinuteOfDay to Calendar, decomposing DayProgress into
a 24x60 in-game clock so games can show a date and time, not just the day
number. Covered by a test.

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

tests/MrGameEng.Core.Tests/CalendarTests.cs

@@ -41,6 +41,19 @@ public class CalendarTests
         Assert.Equal(0.5f, calendar.DayProgress, 5);
     }
 
+    [Fact]
+    public void HourAndMinute_DecomposeTimeOfDay()
+    {
+        var clock = new GameClock();
+        var calendar = new Calendar(clock, secondsPerDay: 1440f); // one minute per in-game minute
+
+        clock.Advance(14 * 60 + 30); // 14:30
+
+        Assert.Equal(14, calendar.Hour);
+        Assert.Equal(30, calendar.Minute);
+        Assert.Equal(14 * 60 + 30, calendar.MinuteOfDay);
+    }
+
     [Fact]
     public void Pause_DoesNotAdvanceTheCalendar()
     {