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>

src/MrGameEng.Core/Calendar.cs

@@ -51,6 +51,15 @@ public sealed class Calendar
             return (float)(days - Math.Floor(days));
         }
     }
+
+    /// <summary>Minutes elapsed in the current day, 0–1439 (a day is 24×60 in-game minutes).</summary>
+    public int MinuteOfDay => (int)(DayProgress * 1440f) % 1440;
+
+    /// <summary>Hour of the current day, 0–23.</summary>
+    public int Hour => MinuteOfDay / 60;
+
+    /// <summary>Minute of the current hour, 0–59.</summary>
+    public int Minute => MinuteOfDay % 60;
 }
 
 /// <summary>Wires the in-game calendar into the engine.</summary>

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()
     {