LANTERN purge B7: rename CharacterId -> FrameKind (frame terminology)

Enum renamed in StatIds.cs (byte values unchanged - serialized definitions/saves
never re-mean); all call sites + doc mentions swept (ClassTraits, PlayerAuthoring,
CharacterStatsDefinition field type, menu/UI, tests). CharacterStatsDefinition SO
CLASS name kept (asset-binding risk; deferred per plan). 390 green.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Assets/_Project/Tests/EditMode/AbilityDatabaseBlobTests.cs

@@ -32,7 +32,7 @@ namespace ProjectM.Tests
             var chars = builder.Allocate(ref root.Characters, 1);
             chars[0] = new CharacterStatsBlob
             {
-                Id = (byte)CharacterId.Default, MoveSpeed = 6f, TurnRateRadiansPerSec = 12.5f,
+                Id = (byte)FrameKind.Default, MoveSpeed = 6f, TurnRateRadiansPerSec = 12.5f,
                 MaxHealth = 100f, Name = "Default"
             };
 
@@ -71,7 +71,7 @@ namespace ProjectM.Tests
             var blob = Build();
             try
             {
-                Assert.IsTrue(blob.Value.TryGetCharacter((byte)CharacterId.Default, out var def));
+                Assert.IsTrue(blob.Value.TryGetCharacter((byte)FrameKind.Default, out var def));
                 Assert.AreEqual(6f, def.MoveSpeed, 1e-4f);
                 Assert.AreEqual(100f, def.MaxHealth, 1e-4f);
                 Assert.AreEqual("Default", def.Name.ToString());