fix(migration): 레거시 개장 시각 센티널 허용

tools/legacy-db-migration/src/game.ts

@@ -83,7 +83,16 @@ const asJsonRecord = (value: JsonValue): Record<string, JsonValue> =>
 export const resolveLegacyGameOpenedAt = (env: JsonValue, legacyDate: Date, context: string): Date => {
     const record = asJsonRecord(env);
     const candidate = record.opentime ?? record.starttime;
-    return candidate === null || candidate === undefined || candidate === '' ? legacyDate : toDate(candidate, context);
+    if (candidate === null || candidate === undefined || candidate === '') {
+        return legacyDate;
+    }
+    try {
+        return toDate(candidate, context);
+    } catch {
+        // 후기 레거시 기수는 개장 전 sentinel(-324000000/0)을 기록하기도 한다.
+        // raw_env는 그대로 보존하고, 유효한 ng_games.date만 파생 시각에 사용한다.
+        return legacyDate;
+    }
 };
 
 const migrateSimpleTable = async (

tools/legacy-db-migration/test/game.test.ts

@@ -114,6 +114,20 @@ describe('legacy archive game migration', () => {
         expect(resolveLegacyGameOpenedAt({}, new Date('2020-01-01T00:00:00.000Z'), 'fixture').toISOString()).toBe(
             '2020-01-01T00:00:00.000Z'
         );
+        expect(
+            resolveLegacyGameOpenedAt(
+                { opentime: -324000000, starttime: 0 },
+                new Date('2026-08-10T22:00:00.000Z'),
+                'fixture'
+            ).toISOString()
+        ).toBe('2026-08-10T22:00:00.000Z');
+        expect(
+            resolveLegacyGameOpenedAt(
+                { opentime: 'not-a-date' },
+                new Date('2026-08-10T22:00:00.000Z'),
+                'fixture'
+            ).toISOString()
+        ).toBe('2026-08-10T22:00:00.000Z');
     });
 
     it('keeps dry-run target-read-only while reporting normalized formats', async () => {