Display player flags next to their names again (#3965)

## Description:

Display flags again.

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

## Please put your Discord username so you can be contacted if a bug or
regression is found:

tryout33

src/client/WebGLFrameBuilder.ts

@@ -1,5 +1,6 @@
 import { Colord } from "colord";
 import { base64url } from "jose";
+import { extractFlagName } from "../core/AssetUrls";
 import { decodePatternData } from "../core/PatternDecoder";
 import { PlayerType } from "../core/game/Game";
 import { GameView } from "../core/game/GameView";
@@ -127,6 +128,11 @@ export class WebGLFrameBuilder {
 
       this.writePaletteEntry(smallID, p.territoryColor(), p.borderColor());
 
+      let flag = p.cosmetics.flag;
+      if (flag) {
+        flag = extractFlagName(flag);
+      }
+
       const pattern = p.cosmetics.pattern;
       if (pattern && pattern.patternData) {
         try {
@@ -148,7 +154,7 @@ export class WebGLFrameBuilder {
 
       newPlayers.push({
         ...p.static,
-        flag: p.cosmetics.flag,
+        flag: flag,
         color: p.territoryColor().toHex(),
       });
     }

src/core/AssetUrls.ts

@@ -100,6 +100,22 @@ export function assetUrl(path: string): string {
   return buildAssetUrl(path, getAssetManifest(), getCdnBase());
 }
 
+/**
+ * Extracts a clean flag name from a cosmetic flag string, which could be
+ * a literal "flag:Name" token or a full CDN URL (e.g. ".../flags/Name.hash.svg").
+ */
+export function extractFlagName(flagData: string): string {
+  if (flagData.startsWith("flag:")) {
+    return flagData.slice(5);
+  }
+  const match = flagData.match(/\/flags\/([^?#]+)\.svg/);
+  if (match) {
+    const raw = match[1].replace(/\.[a-f0-9]{8,12}$/i, "");
+    return safeDecodeAssetSegment(raw);
+  }
+  return flagData;
+}
+
 // Rewrites Vite's emitted /assets/... references in the built index.html to
 // use the cdnBaseRaw EJS placeholder, so RenderHtml.ts can prefix them with
 // CDN_BASE at request time. Scoped to src=/href= attribute values so inline

tests/AssetUrls.test.ts

@@ -1,5 +1,9 @@
 import { describe, expect, test } from "vitest";
-import { buildAssetUrl, rewriteAssetsForCdn } from "../src/core/AssetUrls";
+import {
+  buildAssetUrl,
+  extractFlagName,
+  rewriteAssetsForCdn,
+} from "../src/core/AssetUrls";
 
 describe("AssetUrls", () => {
   test("returns hashed URLs for direct asset matches", () => {
@@ -102,6 +106,41 @@ describe("AssetUrls", () => {
   });
 });
 
+describe("extractFlagName", () => {
+  test("extracts from flag: prefix", () => {
+    expect(extractFlagName("flag:Abbasid Caliphate")).toBe("Abbasid Caliphate");
+  });
+
+  test("extracts and decodes from URL", () => {
+    expect(
+      extractFlagName(
+        "https://cdn.ofedge.dev/game_assets/_assets/flags/Abbasid%20Caliphate.ed17b262829c.svg",
+      ),
+    ).toBe("Abbasid Caliphate");
+    expect(extractFlagName("/flags/Abbasid%20Caliphate.svg")).toBe(
+      "Abbasid Caliphate",
+    );
+  });
+
+  test("returns raw string if not matching flag: or /flags/ URL", () => {
+    expect(extractFlagName("Some Random String")).toBe("Some Random String");
+  });
+
+  test("handles malformed percent-encodings without throwing", () => {
+    expect(extractFlagName("/flags/Bad%C2Encoding.12345678.svg")).toBe(
+      "Bad%C2Encoding",
+    );
+  });
+
+  test("handles edge cases like names containing colons or URLs with hashes", () => {
+    expect(
+      extractFlagName(
+        "/flags/Name%3AWith%3AColons.12345678.svg?query=1#anchor",
+      ),
+    ).toBe("Name:With:Colons");
+  });
+});
+
 describe("rewriteAssetsForCdn", () => {
   test("rewrites src=/assets/ to EJS placeholder", () => {
     const out = rewriteAssetsForCdn(