feat(progression): read surface and change announcements (slice 10a)

reads for the UI: TotalCoins, Lives, IsRunOver, CurrentLevel,
LevelOf/IsOwned/CanAfford, HasCleared. The read half of candidate 01 -
callers get a narrow surface instead of reaching into state.

new domain events LivesChanged / TotalCoinsChanged / SkillSetChanged,
announced by comparing against the last announced value, so an operation
can neither forget to announce nor announce something unchanged.

HandlePlayerDeath now clears the spent attempt - it was still counting
towards TotalCoins after its ledger had been discarded.

republisher and EventBus extended; SkillSetChanged is what SkillManager
will reconcile against instead of the non-atomic call pairs. 65 tests.

Autoloads/EventBus.cs

@@ -164,6 +164,16 @@ public partial class EventBus : Node
     public static void EmitRunEnded()
         => Instance?.EmitSignal(SignalName.RunEnded);
 
+    /// <summary>
+    /// The set of owned skills, or the level of one of them, changed. SkillManager reconciles its live
+    /// components against this instead of every caller remembering to update it separately — the
+    /// non-atomic pair of calls that could leave a skill owned but inert.
+    /// </summary>
+    [Signal] public delegate void SkillSetChangedEventHandler();
+
+    public static void EmitSkillSetChanged()
+        => Instance?.EmitSignal(SignalName.SkillSetChanged);
+
     public static void EmitCoinsChanged(int totalCoins)
         => Instance?.EmitSignal(SignalName.CoinsChanged, totalCoins);
 

Autoloads/ProgressionEventRepublisher.cs

@@ -55,6 +55,18 @@ public sealed class ProgressionEventRepublisher
                 EventBus.EmitAchievementUnlocked(unlocked.Achievement.Value);
                 break;
 
+            case LivesChanged lives:
+                EventBus.EmitLivesChanged(lives.Remaining.Value);
+                break;
+
+            case TotalCoinsChanged coins:
+                EventBus.EmitCoinsChanged(coins.Total.Value);
+                break;
+
+            case SkillSetChanged:
+                EventBus.EmitSkillSetChanged();
+                break;
+
             default:
                 GD.PushWarning($"No signal is published for domain event {@event.GetType().Name}.");
                 break;