Enhance TerritoryLayer with palette signature management

- Added `lastPaletteSignature` to track palette changes.
- Implemented `computePaletteSignature()` to generate a unique signature based on player views and settings.
- Introduced `refreshPaletteIfNeeded()` to refresh the palette when the signature changes, ensuring visual consistency in the TerritoryLayer.

src/client/graphics/layers/TerritoryLayer.ts

@@ -65,6 +65,7 @@ export class TerritoryLayer implements Layer {
 
   private lastFocusedPlayer: PlayerView | null = null;
   private lastMyPlayerSmallId: number | null = null;
+  private lastPaletteSignature: string | null = null;
 
   constructor(
     private game: GameView,
@@ -98,6 +99,7 @@ export class TerritoryLayer implements Layer {
       this.cachedTerritoryPatternsEnabled = patternsEnabled;
       this.redraw();
     }
+    this.refreshPaletteIfNeeded();
 
     this.game.recentlyUpdatedTiles().forEach((t) => {
       this.enqueueTile(t);
@@ -459,6 +461,7 @@ export class TerritoryLayer implements Layer {
       strategy.setHoverHighlightOptions(this.hoverHighlightOptions());
       strategy.setHover(this.highlightedTerritory?.smallID() ?? null);
       this.territoryRenderer = strategy;
+      this.lastPaletteSignature = this.computePaletteSignature();
       return;
     }
 
@@ -467,6 +470,7 @@ export class TerritoryLayer implements Layer {
     this.territoryRenderer.setHoverHighlightOptions(
       this.hoverHighlightOptions(),
     );
+    this.lastPaletteSignature = null;
   }
 
   private hoverHighlightOptions() {
@@ -676,4 +680,24 @@ export class TerritoryLayer implements Layer {
     ctx.fillStyle = radGrad2;
     ctx.fill();
   }
+
+  private computePaletteSignature(): string {
+    let maxSmallId = 0;
+    for (const player of this.game.playerViews()) {
+      maxSmallId = Math.max(maxSmallId, player.smallID());
+    }
+    const patternsEnabled = this.userSettings.territoryPatterns();
+    return `${this.game.playerViews().length}:${maxSmallId}:${patternsEnabled ? 1 : 0}`;
+  }
+
+  private refreshPaletteIfNeeded() {
+    if (!this.territoryRenderer?.isWebGL()) {
+      return;
+    }
+    const signature = this.computePaletteSignature();
+    if (signature !== this.lastPaletteSignature) {
+      this.lastPaletteSignature = signature;
+      this.territoryRenderer.refreshPalette();
+    }
+  }
 }