feat(anon): memorable, collision-proof animal anonymous names (#4611)

## Description:

Makes OpenFront's anonymised names **memorable and collision-proof**.

Anonymised lobbies (e.g. OFM tournaments) previously showed opaque names
— the `Anon420` fallback and hash-derived civ-tribe names in the overlay
— that were hard to remember and could repeat within a viewer's view, so
players couldn't reliably track opponents across a match.

**What changed**
- **`src/core/AnonAnimals.ts`** (new): an 80-word animal bank +
`anonAnimalName(slot, offset)`. Consecutive slots map to **distinct**
handles — the 80 animals fill first (`round 0` → a bare `AnonWolf`),
then a single round digit counts up (`AnonWolf1`, …). At a fixed offset,
two slots can never collide.
- **`GameServer.anonName`**: assigns each player its **join-order slot**
in `allClients` (stable — late-joiners append so existing names never
shift; reconnects reuse their slot) plus a **per-viewer offset**. So
within any one viewer's view no two players can share a name, while
different viewers still see different names for the same player
(**anti-team preserved**). Replaces the old per-pair hash and removes
the now-dead `anonymousUsername` helper.
- **Client fallback** (`genAnonUsername`): draws a random slot through
the same helper (no roster client-side → best-effort); the overlay is
what guarantees uniqueness in-game.
- `createRandomName` (nation/other display names) is untouched.

**Desync safety — audited against #4426**

#4426 fixed a desync where `PlayerExecution` seeded `removeClusters()`
from `player.name()`, a value anonymize-names makes per-client. This
change preserves that invariant:

| Check | Result |
|---|---|
| Deterministic state hash reads `name()`? | **No** — `PlayerImpl.hash =
simpleHash(id)·(troops+numTilesOwned) + Σ unit.hash`; `UnitImpl.hash =
tile + simpleHash(type)·id` |
| `removeClusters` seed | `simpleHash(player.id())` — id-based (#4426
fix), untouched |
| Where `anonName` is called | only `startInfoFor` / `gameInfo` —
per-viewer wire payloads, never the sim |
| Archived record | uses `wireGameStartInfo` (real names) — untouched →
replay/scoring unaffected |
| Net new sim inputs | none — only the display string + server-side
roster order |

The name is display-only and the simulation is name-blind, so this
cannot desync.

**Testing**
- New `tests/AnonAnimals.test.ts`: the no-collision guarantee (250
distinct slots → 250 distinct names), round roll-over, per-viewer
variation, wire-validity/length.
- Existing `tests/server/AnonymizeNames.test.ts` overlay suite still
passes.
- Full suite green locally (`npm test` + `npm run test:coverage`), plus
`build-prod`, `eslint`, and `prettier --check .` clean.

## Please complete the following:

- [x] I have added screenshots for all UI updates — _N/A, no UI changes
(in-game name string only)_
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file — _N/A, generated handles are not
translatable identifiers_
- [x] I have added relevant tests to the test directory —
`tests/AnonAnimals.test.ts`

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

<!-- TODO: fill in Discord username -->

src/core/AnonAnimals.ts

@@ -0,0 +1,104 @@
+// Word bank for anonymous usernames (see genAnonUsername). Each entry is a
+// single, memorable animal word that is username-safe on its own (matches
+// UsernameSchema's [a-zA-Z0-9_ üÜ.] and, prefixed with "Anon" plus one digit,
+// stays under MAX_USERNAME_LENGTH). Kept as recognisable animals with a matching
+// emoji so a future cosmetic pass can pair each name with its animal badge.
+// Order is irrelevant — genAnonUsername indexes into this by a random value.
+export const ANON_ANIMALS: readonly string[] = [
+  "Wolf",
+  "Fox",
+  "Bear",
+  "Panda",
+  "Koala",
+  "Tiger",
+  "Lion",
+  "Leopard",
+  "Cheetah",
+  "Jaguar",
+  "Otter",
+  "Seal",
+  "Sloth",
+  "Raccoon",
+  "Badger",
+  "Skunk",
+  "Hedgehog",
+  "Squirrel",
+  "Hamster",
+  "Rabbit",
+  "Boar",
+  "Horse",
+  "Zebra",
+  "Deer",
+  "Moose",
+  "Bison",
+  "Ram",
+  "Goat",
+  "Camel",
+  "Llama",
+  "Giraffe",
+  "Elephant",
+  "Rhino",
+  "Hippo",
+  "Gorilla",
+  "Orangutan",
+  "Monkey",
+  "Kangaroo",
+  "Bat",
+  "Falcon",
+  "Eagle",
+  "Hawk",
+  "Owl",
+  "Raven",
+  "Swan",
+  "Goose",
+  "Duck",
+  "Chicken",
+  "Rooster",
+  "Penguin",
+  "Flamingo",
+  "Peacock",
+  "Parrot",
+  "Turkey",
+  "Dove",
+  "Shark",
+  "Whale",
+  "Dolphin",
+  "Orca",
+  "Octopus",
+  "Squid",
+  "Crab",
+  "Lobster",
+  "Shrimp",
+  "Pufferfish",
+  "Turtle",
+  "Crocodile",
+  "Snake",
+  "Cobra",
+  "Lizard",
+  "Gecko",
+  "Frog",
+  "Bee",
+  "Butterfly",
+  "Beetle",
+  "Ant",
+  "Spider",
+  "Scorpion",
+  "Snail",
+  "Ladybug",
+];
+
+// "Anon" + animal + optional round number, from a slot index and a per-viewer
+// offset (e.g. "AnonWolf", "AnonFox", … then "AnonWolf1" once all 80 are used).
+// Consecutive slots map to DISTINCT handles: the 80 animals fill first (round 0
+// → a bare name), then the round counts up. So for a fixed offset, two different
+// slots can never collide — that is what lets the anonymisation overlay
+// guarantee unique names by feeding it join-order slots. The offset rotates
+// which animal each slot lands on, so different viewers see a different name for
+// the same player. Output is always wire-valid (letters + optional digits).
+export function anonAnimalName(slot: number, offset = 0): string {
+  const s = Math.abs(Math.trunc(slot));
+  const o = Math.abs(Math.trunc(offset));
+  const animal = ANON_ANIMALS[(s + o) % ANON_ANIMALS.length];
+  const round = Math.floor(s / ANON_ANIMALS.length);
+  return round === 0 ? `Anon${animal}` : `Anon${animal}${round}`;
+}

src/core/Util.ts

@@ -377,18 +377,6 @@ export function createRandomName(
   return randomName;
 }
 
-// Deterministic anonymized username. Reuses createRandomName, then strips the
-// emoji and any illegal chars so it passes UsernameSchema and survives the wire
-// (createRandomName's output is a display string, not a valid username).
-export function anonymousUsername(seed: string): string {
-  const base = createRandomName(seed, PlayerType.Human) ?? "";
-  const name = base
-    .replace(/[^a-zA-Z0-9_ üÜ.]/g, "")
-    .trim()
-    .slice(0, 27);
-  return name.length >= 3 ? name : "Player";
-}
-
 export const emojiTable = [
   ["😀", "😊", "🥰", "😇", "😎"],
   ["😞", "🥺", "😭", "😱", "😡"],