NEO-146: use collection spread in EncounterProgressApi

Apply IDE0305 to defeated-target ordering, assert stable sort in API
tests, and document sorted defeatedTargetIds in Bruno.

bruno/neon-sprawl-server/encounter-progress/Get encounter progress inactive.bru

@@ -7,6 +7,7 @@ meta {
 docs {
   NEO-108: fresh player row before engagement — inactive with empty defeatedTargetIds.
   Pre-request uses combat-targets dev fixture (also clears encounter progress for dev-local-1).
+  Non-empty defeatedTargetIds are returned in stable sorted order.
 }
 
 script:pre-request {

server/NeonSprawl.Server.Tests/Game/Encounters/EncounterProgressApiTests.cs

@@ -124,6 +124,8 @@ public sealed class EncounterProgressApiTests
                 PrototypeNpcRegistry.PrototypeNpcRangedId,
             ],
             row.DefeatedTargetIds);
+        Assert.True(row.DefeatedTargetIds.SequenceEqual(
+            row.DefeatedTargetIds.OrderBy(static id => id, StringComparer.Ordinal)));
         Assert.Null(row.CompletedAt);
         Assert.Null(row.RewardGrantSummary);
         var completionStore = factory.Services.GetRequiredService<IEncounterCompletionStore>();

server/NeonSprawl.Server/Game/Encounters/EncounterProgressApi.cs

@@ -72,7 +72,7 @@ public static class EncounterProgressApi
     {
         var hasProgress = progressStore.TryGetProgress(playerId, encounterId, out var progress);
         var defeatedTargetIds = hasProgress
-            ? progress.DefeatedNpcInstanceIds.OrderBy(static id => id, StringComparer.Ordinal).ToArray()
+            ? [.. progress.DefeatedNpcInstanceIds.OrderBy(static id => id, StringComparer.Ordinal)]
             : Array.Empty<string>();
 
         if (completionStore.IsCompleted(playerId, encounterId))