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.

game/internal/controller/report_test.go

@@ -196,3 +196,34 @@ func TestReportIncomingGroupRemainingDistance(t *testing.T) {
 	// route would be sqrt(2) ≈ 1.414.
 	assert.InDelta(t, 5.657, rep.IncomingGroup[0].Distance.F(), 0.01)
 }
+
+// TestReportExitWarnings checks the inactivity-removal warnings: the recipient
+// gets a personal countdown only at TTL 1..5, other non-extinct races within 3
+// turns are listed publicly, the recipient is excluded from its own public
+// list, and extinct races never appear.
+func TestReportExitWarnings(t *testing.T) {
+	c, _ := newCache()
+	c.Race(Race_0_idx).TTL = 5
+	c.Race(Race_1_idx).TTL = 2
+	c.Race(2).TTL = 2 // Race_Extinct: extinct, must never appear publicly
+
+	// Race_0's report: personal countdown 5; only Race_1 (TTL 2) is public.
+	r0 := &report.Report{}
+	c.ReportExitWarnings(Race_0_idx, r0)
+	assert.Equal(t, uint(5), r0.PersonalExitWarning)
+	assert.Len(t, r0.RacesLeavingSoon, 1)
+	assert.Equal(t, Race_1.Name, r0.RacesLeavingSoon[0].Race)
+	assert.Equal(t, uint(2), r0.RacesLeavingSoon[0].TurnsLeft)
+
+	// Race_1's report: personal countdown 2; Race_0 (TTL 5 > 3) is not public.
+	r1 := &report.Report{}
+	c.ReportExitWarnings(Race_1_idx, r1)
+	assert.Equal(t, uint(2), r1.PersonalExitWarning)
+	assert.Empty(t, r1.RacesLeavingSoon)
+
+	// TTL above the 5-turn window → no personal warning.
+	c.Race(Race_0_idx).TTL = 6
+	r0b := &report.Report{}
+	c.ReportExitWarnings(Race_0_idx, r0b)
+	assert.Zero(t, r0b.PersonalExitWarning)
+}