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/src/lib/active-view/report/section-race-exit-warnings.svelte

@@ -0,0 +1,70 @@
+<!--
+Report View — races leaving soon section. Surfaces the public
+`racesLeavingSoon` projection: every other race within three turns of
+being auto-removed for inactivity, with the number of turns each has
+left. This is the public counterpart to the personal exit-warning
+banner the report view renders at the top for the local race.
+
+Unlike the other report sections, this one hides entirely when the
+list is empty rather than showing an empty-state line: an absent
+notice is the normal, healthy case for an active game, so a permanent
+"no races leaving" row would be noise. The section's TOC entry stays
+registered; clicking it while the section is hidden is a silent no-op
+through the table-of-contents' existing `getElementById` guard.
+-->
+<script lang="ts">
+	import { getContext } from "svelte";
+
+	import { i18n } from "$lib/i18n/index.svelte";
+	import {
+		RENDERED_REPORT_CONTEXT_KEY,
+		type RenderedReportSource,
+	} from "$lib/rendered-report.svelte";
+
+	const rendered = getContext<RenderedReportSource | undefined>(
+		RENDERED_REPORT_CONTEXT_KEY,
+	);
+	const report = $derived(rendered?.report ?? null);
+	const rows = $derived(report?.racesLeavingSoon ?? []);
+</script>
+
+{#if rows.length > 0}
+	<section
+		id="report-race-exit-warnings"
+		class="grid-section"
+		data-testid="report-section-race-exit-warnings"
+	>
+		<h2>{i18n.t("game.report.section.race_exit_warnings.title")}</h2>
+
+		<ul class="notices" data-testid="race-exit-warnings-list">
+			{#each rows as r (r.race)}
+				<li data-testid="race-exit-warnings-row" data-race={r.race}>
+					{i18n.t("game.report.section.race_exit_warnings.notice", {
+						race: r.race,
+						turns: String(r.turnsLeft),
+					})}
+				</li>
+			{/each}
+		</ul>
+	</section>
+{/if}
+
+<style>
+	.grid-section h2 {
+		margin: 0 0 0.5rem;
+		font-size: 1.05rem;
+		color: var(--color-text);
+	}
+	.notices {
+		margin: 0;
+		padding-left: 1.1rem;
+		display: flex;
+		flex-direction: column;
+		gap: 0.3rem;
+		font-size: 0.9rem;
+		color: var(--color-warning);
+	}
+	.notices li {
+		margin: 0;
+	}
+</style>