ui/phase-27: battle viewer (radial scene, playback, map markers)

Engine wire change: Report.battle switched from []uuid.UUID to
[]BattleSummary{id, planet, shots} so the map can place battle
markers without N extra fetches. FBS schema + generated Go/TS
regenerated; transcoder + report controller updated; openapi
adds the BattleSummary schema with a freeze test.

Backend gateway forwards engine GET /api/v1/battle/:turn/:uuid as
/api/v1/user/games/{game_id}/battles/{turn}/{battle_id} (handler
plus engineclient.FetchBattle, contract test stub, openapi spec).

UI:
- BattleViewer (lib/battle-player/) is a logically isolated SVG
  radial scene that consumes a BattleReport prop. Planet at the
  centre, races on the outer ring at equal angular spacing, race
  clusters by (race, className) with <class>:<numLeft> labels;
  observer groups (inBattle: false) are not drawn; eliminated
  races drop out and survivors re-distribute on the next frame.
- Shot line per frame: red on destroyed, green otherwise; erased
  on the next frame. Playback controls: play/pause + step ± +
  rewind + 1x/2x/4x speed (400/200/100 ms per frame).
- Page wrapper (lib/active-view/battle.svelte) loads BattleReport
  via api/battle-fetch.ts; synthetic-gameId prefix routes to a
  fixture loader, otherwise REST through the gateway. Always-
  visible <ol> text protocol satisfies the accessibility ask.
- section-battles.svelte links every battle UUID into the viewer.
- map/battle-markers.ts: yellow X cross of 2 LinePrim through the
  corners of the planet's circumscribed square (stroke width
  clamps from 1 px at 1 shot to 5 px at 100+ shots); bombing
  marker is a stroke-only ring (yellow when damaged, red when
  wiped). Wired into state-binding.ts; click handler dispatches
  battle clicks to the viewer and bombing clicks to the matching
  Reports row.
- i18n keys for the viewer in en + ru.

Docs: ui/docs/battle-viewer-ux.md, FUNCTIONAL.md §6.5 + ru
mirror, ui/PLAN.md Phase 27 decisions + deferred TODOs (push
event, richer class visuals, animated re-distribution).

Tests: Vitest unit (radial layout + timeline frame builder +
marker stroke formula + marker primitives), Playwright e2e for
the viewer (Reports link → viewer, playback step, not-found),
backend engineclient FetchBattle (200 / 404 / bad input), engine
openapi freezes (BattleReport, BattleReportGroup,
BattleActionReport, BattleSummary, Report.battle items).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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

@@ -19,6 +19,7 @@ import { Builder } from "flatbuffers";
 
 import { UUID } from "../../../src/proto/galaxy/fbs/common";
 import {
+	BattleSummary,
 	Bombing,
 	LocalPlanet,
 	OtherPlanet,
@@ -108,6 +109,12 @@ export interface OtherShipClassFixture extends ShipClassFixture {
 	mass?: number;
 }
 
+export interface BattleSummaryFixture {
+	id: string;
+	planet: number;
+	shots: number;
+}
+
 export interface BombingFixture {
 	planetNumber: number;
 	planet: string;
@@ -149,7 +156,7 @@ export interface ReportFixture {
 	myVoteFor?: string;
 	otherScience?: OtherScienceFixture[];
 	otherShipClass?: OtherShipClassFixture[];
-	battles?: string[];
+	battles?: BattleSummaryFixture[];
 	bombings?: BombingFixture[];
 	shipProductions?: ShipProductionFixture[];
 }
@@ -397,17 +404,22 @@ export function buildReportPayload(fixture: ReportFixture): Uint8Array {
 		shipProductionOffsets.length === 0
 			? null
 			: Report.createShipProductionVector(builder, shipProductionOffsets);
-	// `battle` is a struct vector (16 bytes per UUID, alignment 8), so
-	// it uses the start/inline-write/end pattern rather than a typical
-	// offset-list helper. Iterating in reverse matches the FlatBuffers
-	// convention that the vector is built end-to-start.
+	// Phase 27 — `battle` carries `BattleSummary` tables, each with
+	// an inline `id:UUID` struct plus `planet` and `shots` slots.
 	const battleVec = (() => {
-		const ids = fixture.battles ?? [];
-		if (ids.length === 0) return null;
-		Report.startBattleVector(builder, ids.length);
-		for (let i = ids.length - 1; i >= 0; i--) {
-			const [hi, lo] = uuidToHiLo(ids[i]!);
-			UUID.createUUID(builder, hi, lo);
+		const summaries = fixture.battles ?? [];
+		if (summaries.length === 0) return null;
+		const offsets = summaries.map((s) => {
+			const [hi, lo] = uuidToHiLo(s.id);
+			BattleSummary.startBattleSummary(builder);
+			BattleSummary.addId(builder, UUID.createUUID(builder, hi, lo));
+			BattleSummary.addPlanet(builder, BigInt(s.planet));
+			BattleSummary.addShots(builder, BigInt(s.shots));
+			return BattleSummary.endBattleSummary(builder);
+		});
+		Report.startBattleVector(builder, offsets.length);
+		for (let i = offsets.length - 1; i >= 0; i--) {
+			builder.addOffset(offsets[i]);
 		}
 		return builder.endVector();
 	})();