make spawn glow follow the player's currently selected spawn tile

Plumb spawnTile through PlayerUpdate / PlayerState / applyStateUpdate
so the WebGL spawn overlay can read it directly. The glow was reading
nameData.x/y (territory centroid for label placement) which only
recomputes every 2 ticks and only when largestClusterBoundingBox has
been updated by PlayerExecution — both lag the player's actual spawn
click. Using spawnTile updates the same tick setSpawnTile() fires.

Also adds spawnTile to diffPlayerUpdate / applyStateUpdate so changes
after the initial full snapshot actually propagate (the recent
diff-only PlayerUpdate path silently dropped any field not enumerated
in those helpers).

src/client/render/types/Renderer.ts

@@ -61,6 +61,8 @@ export interface PlayerState {
   traitorRemainingTicks: number;
   betrayals: number;
   hasSpawned: boolean;
+  /** TileRef the player picked as their spawn (undefined if not yet spawned). */
+  spawnTile?: number;
   lastDeleteUnitTick: number;
   allies: number[];
   embargoes: number[];