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/Scripts/Server/Connection/GoInGameServerSystem.cs

@@ -101,7 +101,7 @@ namespace ProjectM.Server
                 // meta-band StatModifiers on the just-instantiated player (same ECB as Instantiate, the
                 // ClassTraits idiom). Skip tier 0 / unknown ids (preserve-don't-crash); CLAMP a saved tier above a
                 // rebalanced MaxTier (D-F5). Class gate via BoonMath.MaskFor (ClassId is the normalized
-                // CharacterId 2/3 — a raw 1<<ClassId would compute bits 2/3 and silently skip everything).
+                // FrameKind 2/3 — a raw 1<<ClassId would compute bits 2/3 and silently skip everything).
                 if (!isGym)
                 {
                     ref var metaPool = ref metaCatalog.Value.Value;