Add Timelines.All shortcut

MultiversalDiplomacy/Model/Timelines.cs

@@ -66,11 +66,17 @@ public class Timelines(int next, Dictionary<string, Season?> pasts)
     public int Next { get; private set; } = next;
 
     /// <summary>
-    /// Map of season designations to their parent seasons.
-    /// The set of keys here is the set of all seasons in the multiverse.
+    /// Map of season designations to their parent seasons. Every season has an entry, so
+    /// the set of keys is the set of existing seasons.
     /// </summary>
     public Dictionary<string, Season?> Pasts { get; } = pasts;
 
+    /// <summary>
+    /// All seasons in the multiverse.
+    /// </summary>
+    [JsonIgnore]
+    public IEnumerable<Season> Seasons => Pasts.Keys.Select(key => new Season(key));
+
     /// <summary>
     /// Create a new multiverse with an initial season.
     /// </summary>

MultiversalDiplomacyTests/MDATC_A.cs

@@ -33,11 +33,11 @@ public class TimeTravelTest
 
         // Confirm that there are now four seasons: three in the main timeline and one in a fork.
         Assert.That(
-            world.Timelines.Pasts.Keys.Select(key => new Season(key)).Where(s => s.Timeline == s0.Timeline).Count(),
+            world.Timelines.Seasons.Where(s => s.Timeline == s0.Timeline).Count(),
             Is.EqualTo(3),
             "Failed to advance main timeline after last unit left");
         Assert.That(
-            world.Timelines.Pasts.Keys.Select(key => new Season(key)).Where(s => s.Timeline != s0.Timeline).Count(),
+            world.Timelines.Seasons.Where(s => s.Timeline != s0.Timeline).Count(),
             Is.EqualTo(1),
             "Failed to fork timeline when unit moved in");