battle-viewer e2e: mock user.games.battle ConnectRPC command

Phase 28 moved the battle fetch off the REST passthrough onto the
signed envelope, so the Playwright spec's `page.route(...)` against
the old REST path no longer intercepts anything and the viewer
times out waiting for data. Update the spec to:

- Build a FlatBuffers `BattleReport` payload in
  `fixtures/battle-fbs.ts` (mirrors `report-fbs.ts`'s pattern).
- Add a `user.games.battle` case to the ExecuteCommand mock that
  decodes the FBS `GameBattleRequest`, returns the encoded report
  when the battle_id matches the seeded one, and surfaces a
  canonical `not_found` resultCode otherwise.
- Drop the obsolete REST route stubs.
- Drive the negative-path test with a real UUID that does not match
  the seeded one, so the gateway-side switch is the source of the
  404 (the old `missing-uuid` literal was no longer a valid wire
  shape for the UUID decoder).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

ui/frontend/tests/e2e/fixtures/battle-fbs.ts

@@ -0,0 +1,128 @@
+// Phase 28 — FBS BattleReport payload builder used by Battle Viewer
+// Playwright specs. Mirrors the `user.games.battle` ConnectRPC
+// response that the gateway re-encodes from the engine's JSON.
+
+import { Builder } from "flatbuffers";
+
+import {
+	BattleActionReport,
+	BattleReport,
+	BattleReportGroup,
+	RaceEntry,
+	ShipEntry,
+	TechEntry,
+	UUID,
+} from "../../../src/proto/galaxy/fbs/battle";
+
+export interface BattleGroupFixture {
+	key: number;
+	race: string;
+	className: string;
+	tech?: Record<string, number>;
+	num: number;
+	numLeft: number;
+	loadType?: string;
+	loadQuantity?: number;
+	inBattle?: boolean;
+}
+
+export interface BattleActionFixture {
+	a: number;
+	sa: number;
+	d: number;
+	sd: number;
+	x: boolean;
+}
+
+export interface BattleFixture {
+	id: string;
+	planet: number;
+	planetName: string;
+	races: Record<string, string>;
+	ships: BattleGroupFixture[];
+	protocol: BattleActionFixture[];
+}
+
+export function buildBattlePayload(fixture: BattleFixture): Uint8Array {
+	const builder = new Builder(512);
+
+	const planetNameOff = builder.createString(fixture.planetName);
+
+	const raceOffsets: number[] = [];
+	for (const [keyStr, value] of Object.entries(fixture.races)) {
+		const key = Number(keyStr);
+		const [hi, lo] = uuidToHiLo(value);
+		RaceEntry.startRaceEntry(builder);
+		RaceEntry.addKey(builder, BigInt(key));
+		RaceEntry.addValue(builder, UUID.createUUID(builder, hi, lo));
+		raceOffsets.push(RaceEntry.endRaceEntry(builder));
+	}
+	const racesVec = BattleReport.createRacesVector(builder, raceOffsets);
+
+	const shipOffsets: number[] = [];
+	for (const ship of fixture.ships) {
+		const techOffsets: number[] = [];
+		for (const [tk, tv] of Object.entries(ship.tech ?? {})) {
+			const tkOff = builder.createString(tk);
+			TechEntry.startTechEntry(builder);
+			TechEntry.addKey(builder, tkOff);
+			TechEntry.addValue(builder, tv);
+			techOffsets.push(TechEntry.endTechEntry(builder));
+		}
+		const techVec = BattleReportGroup.createTechVector(builder, techOffsets);
+		const raceStrOff = builder.createString(ship.race);
+		const classNameOff = builder.createString(ship.className);
+		const loadTypeOff = builder.createString(ship.loadType ?? "");
+		BattleReportGroup.startBattleReportGroup(builder);
+		BattleReportGroup.addInBattle(builder, ship.inBattle ?? true);
+		BattleReportGroup.addNumber(builder, BigInt(ship.num));
+		BattleReportGroup.addNumberLeft(builder, BigInt(ship.numLeft));
+		BattleReportGroup.addLoadQuantity(builder, ship.loadQuantity ?? 0);
+		BattleReportGroup.addTech(builder, techVec);
+		BattleReportGroup.addRace(builder, raceStrOff);
+		BattleReportGroup.addClassName(builder, classNameOff);
+		BattleReportGroup.addLoadType(builder, loadTypeOff);
+		const groupOff = BattleReportGroup.endBattleReportGroup(builder);
+		ShipEntry.startShipEntry(builder);
+		ShipEntry.addKey(builder, BigInt(ship.key));
+		ShipEntry.addValue(builder, groupOff);
+		shipOffsets.push(ShipEntry.endShipEntry(builder));
+	}
+	const shipsVec = BattleReport.createShipsVector(builder, shipOffsets);
+
+	const protocolOffsets: number[] = [];
+	for (const action of fixture.protocol) {
+		BattleActionReport.startBattleActionReport(builder);
+		BattleActionReport.addAttacker(builder, BigInt(action.a));
+		BattleActionReport.addAttackerShipClass(builder, BigInt(action.sa));
+		BattleActionReport.addDefender(builder, BigInt(action.d));
+		BattleActionReport.addDefenderShipClass(builder, BigInt(action.sd));
+		BattleActionReport.addDestroyed(builder, action.x);
+		protocolOffsets.push(BattleActionReport.endBattleActionReport(builder));
+	}
+	const protocolVec = BattleReport.createProtocolVector(
+		builder,
+		protocolOffsets,
+	);
+
+	const [idHi, idLo] = uuidToHiLo(fixture.id);
+	BattleReport.startBattleReport(builder);
+	BattleReport.addId(builder, UUID.createUUID(builder, idHi, idLo));
+	BattleReport.addPlanet(builder, BigInt(fixture.planet));
+	BattleReport.addPlanetName(builder, planetNameOff);
+	BattleReport.addRaces(builder, racesVec);
+	BattleReport.addShips(builder, shipsVec);
+	BattleReport.addProtocol(builder, protocolVec);
+	builder.finish(BattleReport.endBattleReport(builder));
+	return builder.asUint8Array();
+}
+
+function uuidToHiLo(value: string): [bigint, bigint] {
+	const hex = value.replace(/-/g, "").toLowerCase();
+	if (hex.length !== 32 || /[^0-9a-f]/.test(hex)) {
+		throw new Error(`buildBattlePayload: invalid uuid ${value}`);
+	}
+	const hi = BigInt(`0x${hex.slice(0, 16)}`);
+	const lo = BigInt(`0x${hex.slice(16, 32)}`);
+	return [hi, lo];
+}