fix(stats): stop estimating sessions from KOReader progress

Keep KOSync limited to position synchronization and rely on measured page timings from the BookOrbit plugin for KOReader reading sessions. Remove legacy estimates at startup and rebuild affected daily totals.

Fixes #1233

server/test/koreader-progress-position.e2e-spec.ts

@@ -1,7 +1,8 @@
 import { randomUUID } from 'crypto';
-import { eq } from 'drizzle-orm';
+import { and, eq } from 'drizzle-orm';
 
 import * as schema from '../src/db/schema';
+import { ReadingSessionService } from '../src/modules/reading-session/reading-session.service';
 import { createCbzFixture, createEpubFixture } from './e2e/reader-state-isolation/reader-state-isolation-fixture-builder';
 import {
   authHeader,
@@ -18,6 +19,7 @@ import {
 const KOREADER_USERNAME = `progress-position-device-${randomUUID().slice(0, 8)}`;
 const KOREADER_PASSWORD = 'ProgressPositionPass123';
 const XPOINTER = '/body/DocFragment[8]/body/p[12]/text().0';
+const DEVICE_ID = 'progress-regression-device';
 
 /**
  * KOReader reports a paged document's position as a page number and a reflowable one's as an
@@ -47,7 +49,13 @@ describe('KOReader progress position routing (e2e)', { timeout: 180_000 }, () =>
       method: 'PUT',
       url: '/api/v1/koreader/syncs/progress',
       headers: deviceHeaders(),
-      payload: { document: hash, percentage, ...(progress === undefined ? {} : { progress }) },
+      payload: {
+        document: hash,
+        percentage,
+        device: 'Regression device',
+        device_id: DEVICE_ID,
+        ...(progress === undefined ? {} : { progress }),
+      },
     });
     expect(response.statusCode).toBe(200);
   }
@@ -159,6 +167,8 @@ describe('KOReader progress position routing (e2e)', { timeout: 180_000 }, () =>
         document: epubHash,
         percentage: 0.35,
         progress: XPOINTER,
+        device: 'Regression device',
+        device_id: DEVICE_ID,
         metadata: { filename: 'progress-position-book.epub', title: 'Progress Position Book', authors: 'Test Author' },
       },
     });
@@ -194,6 +204,61 @@ describe('KOReader progress position routing (e2e)', { timeout: 180_000 }, () =>
     expect(stored?.percentage).toBeCloseTo(80, 5);
   });
 
+  it('never turns KOSync progress pushes into reading sessions', async () => {
+    await syncFromDevice(epubHash, 0.4, XPOINTER);
+    await ctx.db
+      .update(schema.koreaderDeviceProgress)
+      .set({ updatedAt: new Date(Date.now() - 12 * 60 * 1000) })
+      .where(and(eq(schema.koreaderDeviceProgress.bookFileId, epub.bookFileId), eq(schema.koreaderDeviceProgress.deviceId, DEVICE_ID)));
+
+    await syncFromDevice(epubHash, 0.5, XPOINTER);
+
+    const sessions = await ctx.db
+      .select({ id: schema.readingSessions.id })
+      .from(schema.readingSessions)
+      .where(and(eq(schema.readingSessions.bookFileId, epub.bookFileId), eq(schema.readingSessions.source, 'koreader')));
+    expect(sessions).toEqual([]);
+  });
+
+  it('removes only historical KOSync estimates during repair', async () => {
+    const [koreaderUser] = await ctx.db
+      .select({ userId: schema.koreaderUsers.userId })
+      .from(schema.koreaderUsers)
+      .where(eq(schema.koreaderUsers.username, KOREADER_USERNAME));
+    expect(koreaderUser).toBeDefined();
+
+    const legacySessionId = `ks-${'a'.repeat(12)}-${'b'.repeat(32)}`;
+    const measuredSessionId = 'kor:cleanup-supported';
+    const webSessionId = 'web-cleanup-supported';
+    const startedAt = new Date('2026-08-31T10:00:00.000Z');
+    const endedAt = new Date('2026-08-31T10:10:00.000Z');
+    await ctx.db.insert(schema.readingSessions).values(
+      [
+        { sessionId: legacySessionId, source: 'koreader' as const },
+        { sessionId: measuredSessionId, source: 'koreader' as const },
+        { sessionId: webSessionId, source: 'web' as const },
+      ].map((session) => ({
+        ...session,
+        userId: koreaderUser!.userId,
+        bookId: epub.bookId,
+        bookFileId: epub.bookFileId,
+        startedAt,
+        endedAt,
+        durationSeconds: 600,
+        progressDelta: 2,
+        endProgress: 50,
+      })),
+    );
+
+    await expect(ctx.app.get(ReadingSessionService).deleteLegacyKoreaderSyncEstimatesBatch(500)).resolves.toEqual({ deleted: 1 });
+
+    const remaining = await ctx.db
+      .select({ sessionId: schema.readingSessions.sessionId })
+      .from(schema.readingSessions)
+      .where(and(eq(schema.readingSessions.userId, koreaderUser!.userId), eq(schema.readingSessions.bookFileId, epub.bookFileId)));
+    expect(remaining.map((row) => row.sessionId).sort()).toEqual([measuredSessionId, webSessionId].sort());
+  });
+
   it('does not route progress when the document hash matches different books', async () => {
     const comicProgressBefore = await storedProgress(comic.bookFileId);
     const epubProgressBefore = await storedProgress(epub.bookFileId);