feat(game): race exit warnings in the turn report (#12)

Surface the inactivity-removal countdown the rules promise but the
engine never reported. A race within five turns of being auto-removed
for inactivity gets a personal warning in its own report; every race
within three turns is listed publicly to all participants.

- model: Report.PersonalExitWarning + RacesLeavingSoon ([]RaceExitNotice)
- fbs: RaceExitNotice table + Report.personal_exit_warning /
  races_leaving_soon (regenerated Go + TS bindings)
- transcoder: encode/decode both fields
- engine: ReportExitWarnings fills the recipient's TTL (1..5) and lists
  other non-extinct races with TTL 1..3, excluding the recipient itself
- ui: danger-styled personal banner + "races leaving soon" section
  (hidden when empty), wired into the report view, EN/RU i18n
- docs: rules.txt report-section list, FUNCTIONAL.md 6.4 + RU mirror

Voluntary quit and idle timeout share the TTL countdown and are not
distinguished, per the agreed scope.

ui/frontend/tests/helpers/empty-ship-groups.ts

@@ -1,8 +1,10 @@
 // EMPTY_SHIP_GROUPS supplies empty arrays / zero defaults for the
 // ancillary report fields added in Phase 19 (ship-groups + fleets),
-// Phase 21 (sciences), Phase 22 (races / diplomacy / voting), and
+// Phase 21 (sciences), Phase 22 (races / diplomacy / voting),
 // Phase 23 (full player roster, foreign sciences, foreign ship
-// classes, battle ids, bombings, ships in production).
+// classes, battle ids, bombings, ships in production), and the
+// per-turn inactivity exit warnings (personal countdown + public
+// races-leaving-soon list).
 // Test fixtures spread it into their report objects so the fixture
 // body still focuses on the fields under test, without forcing
 // every spec to enumerate the full GameReport surface.
@@ -41,6 +43,8 @@ export const EMPTY_SHIP_GROUPS: {
 	battleIds: string[];
 	bombings: ReportBombing[];
 	shipProductions: ReportShipProduction[];
+	personalExitWarning: number;
+	racesLeavingSoon: { race: string; turnsLeft: number }[];
 } = {
 	localShipGroups: [],
 	otherShipGroups: [],
@@ -59,4 +63,6 @@ export const EMPTY_SHIP_GROUPS: {
 	battleIds: [],
 	bombings: [],
 	shipProductions: [],
+	personalExitWarning: 0,
+	racesLeavingSoon: [],
 };