Use shared local-day helpers in immersion tracker tests

- derive midnight and week-boundary timestamps from query-shared utilities
- keep split-module coverage aligned with db-local time handling

src/core/services/immersion-tracker/__tests__/query-split-modules.test.ts

@@ -50,6 +50,7 @@ import {
   updateAnimeAnilistInfo,
   upsertCoverArt,
 } from '../query-maintenance.js';
+import { getLocalEpochDay } from '../query-shared.js';
 import { EVENT_CARD_MINED, EVENT_SUBTITLE_LINE, SOURCE_TYPE_LOCAL } from '../types.js';
 
 function makeDbPath(): string {
@@ -360,9 +361,6 @@ test('split library helpers return anime/media session and analytics rows', () =
 
   try {
     const now = new Date();
-    const todayLocalDay = Math.floor(
-      new Date(now.getFullYear(), now.getMonth(), now.getDate()).getTime() / 86_400_000,
-    );
     const animeId = getOrCreateAnimeRecord(db, {
       parsedTitle: 'Library Anime',
       canonicalTitle: 'Library Anime',
@@ -398,6 +396,7 @@ test('split library helpers return anime/media session and analytics rows', () =
       0,
     ).getTime();
     const sessionId = startSessionRecord(db, videoId, startedAtMs).sessionId;
+    const todayLocalDay = getLocalEpochDay(db, startedAtMs);
     finalizeSessionMetrics(db, sessionId, startedAtMs, {
       endedAtMs: startedAtMs + 55_000,
       totalWatchedMs: 55_000,

src/core/services/immersion-tracker/__tests__/query.test.ts

@@ -37,6 +37,11 @@ import {
   getWordOccurrences,
   upsertCoverArt,
 } from '../query.js';
+import {
+  getShiftedLocalDaySec,
+  getStartOfLocalDayTimestamp,
+  toDbTimestamp,
+} from '../query-shared.js';
 import {
   SOURCE_TYPE_LOCAL,
   SOURCE_TYPE_REMOTE,
@@ -44,7 +49,6 @@ import {
   EVENT_SUBTITLE_LINE,
   EVENT_YOMITAN_LOOKUP,
 } from '../types.js';
-import { toDbTimestamp } from '../query-shared.js';
 
 function makeDbPath(): string {
   const dir = fs.mkdtempSync(path.join(os.tmpdir(), 'subminer-imm-query-test-'));
@@ -728,8 +732,9 @@ test('getTrendsDashboard keeps local-midnight session buckets separate', () => {
       parseMetadataJson: null,
     });
 
-    const beforeMidnight = '1772436600000';
+    const boundaryMs = BigInt(getStartOfLocalDayTimestamp(db, '1772436600000'));
-    const afterMidnight = '1772440200000';
+    const beforeMidnight = (boundaryMs - 1n).toString();
+    const afterMidnight = (boundaryMs + 1n).toString();
     const firstSessionId = 1;
     const secondSessionId = 2;
     const insertSession = db.prepare(
@@ -1135,8 +1140,9 @@ test('getQueryHints computes weekly new-word cutoff from calendar midnights', ()
         ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
         `,
       );
-      const justBeforeWeekBoundary = 1_772_955_000;
+      const weekBoundarySec = getShiftedLocalDaySec(db, '1773601200000', -7);
-      const justAfterWeekBoundary = 1_772_958_600;
+      const justBeforeWeekBoundary = weekBoundarySec - 1;
+      const justAfterWeekBoundary = weekBoundarySec + 1;
       insertWord.run(
         '境界前',
         '境界前',