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>

pkg/model/report/battle.go

@@ -6,6 +6,16 @@ import (
 	"github.com/google/uuid"
 )
 
+// BattleSummary identifies one battle relevant to the report recipient
+// and carries the data needed to render a battle marker on the map
+// without fetching the full BattleReport. Planet locates the marker;
+// Shots scales the marker stroke with the battle length.
+type BattleSummary struct {
+	ID     uuid.UUID `json:"id"`
+	Planet uint      `json:"planet"`
+	Shots  uint      `json:"shots"`
+}
+
 type BattleReport struct {
 	// Battle unique ID
 	ID uuid.UUID `json:"id"`

pkg/model/report/report.go

@@ -33,7 +33,7 @@ type Report struct {
 	OtherScience       []OtherScience       `json:"otherScience,omitempty"`
 	LocalShipClass     []ShipClass          `json:"localShipClass,omitempty"`
 	OtherShipClass     []OthersShipClass    `json:"otherShipClass,omitempty"`
-	Battle             []uuid.UUID          `json:"battle,omitempty"`
+	Battle             []BattleSummary      `json:"battle,omitempty"`
 	Bombing            []*Bombing           `json:"bombing,omitempty"`
 	IncomingGroup      []IncomingGroup      `json:"incomingGroup,omitempty"`
 	LocalPlanet        []LocalPlanet        `json:"localPlanet,omitempty"`