Preserve fleet match timing across empty telemetry

tests/unit/server-observation.test.ts

@@ -434,7 +434,7 @@ describe('shared server observation', () => {
         expect(freshTelemetry({ ...report(), players: [{}] } as never, now)).toBe(false);
     });
 
-    it('uses game-start rosters without inventing scores and clears match times on an empty report', () => {
+    it('uses game-start rosters without inventing scores and preserves match times on an empty report', () => {
         const start = { ...gameEvent('game_start', 0, 2, 'managed'), receivedAt: at() };
         const active = selectServerObservation(server(), start, now);
         expect(active.roster?.[0]).toMatchObject({ score: null, ping: null });
@@ -444,8 +444,8 @@ describe('shared server observation', () => {
         ).toMatchObject({
             last_players: 0,
             roster: [],
-            game_started_at: null,
-            game_ended_at: null
+            game_started_at: at(),
+            game_ended_at: at()
         });
     });
 });