mod: restore missing mod features from resync audit

Re-add KOReaderSyncActivity PUSH_ONLY mode (PR #1090):
- SyncMode enum with INTERACTIVE/PUSH_ONLY, deferFinish pattern
- Push & Sleep menu action in EpubReaderMenuActivity
- ActivityManager::requestSleep() for activity-initiated sleep
- main.cpp checks isSleepRequested() each loop iteration

Wire EndOfBookMenuActivity into EpubReaderActivity:
- pendingEndOfBookMenu deferred flag avoids render-lock deadlock
- Handles all 6 actions: ARCHIVE, DELETE, TABLE_OF_CONTENTS,
  BACK_TO_BEGINNING, CLOSE_BOOK, CLOSE_MENU

Add book management to reader menu:
- ARCHIVE_BOOK, DELETE_BOOK, REINDEX_BOOK actions with handlers

Port silent next-chapter pre-indexing:
- silentIndexNextChapterIfNeeded() proactively indexes next chapter
  when user is near end of current one, eliminating load screens

Add per-book letterbox fill toggle in reader menu:
- LETTERBOX_FILL cycles Default/Dithered/Solid/None
- Loads/saves per-book override via BookSettings
- bookCachePath constructor param added to EpubReaderMenuActivity

Made-with: Cursor

chat-summaries/2026-03-07_20-00-summary.md

@@ -0,0 +1,61 @@
+# Missing Mod Features Audit — Implementation
+
+**Date**: 2026-03-07
+**Branch**: `mod/master-resync`
+
+## Task
+
+Comprehensive audit of `mod/master-resync` vs `mod/backup-pre-sync-2026-03-07` identified 4 mod features lost during the upstream resync. All 4 have been re-implemented.
+
+## Changes
+
+### 1. EndOfBookMenuActivity wired into EpubReaderActivity (HIGH)
+
+**Files**: `EpubReaderActivity.h`, `EpubReaderActivity.cpp`
+
+- Added `pendingEndOfBookMenu` and `endOfBookMenuOpened` flags
+- In `render()`: when reaching end-of-book, sets `pendingEndOfBookMenu = true` (deferred to avoid render-lock deadlock)
+- In `loop()`: checks flag and launches `EndOfBookMenuActivity` via `startActivityForResult`
+- Result handler covers all 6 actions: ARCHIVE (→ goHome), DELETE (→ goHome), TABLE_OF_CONTENTS (→ last chapter), BACK_TO_BEGINNING (→ spine 0), CLOSE_BOOK (→ goHome), CLOSE_MENU (→ stay at end)
+- Added `#include "EndOfBookMenuActivity.h"` and `#include "util/BookManager.h"`
+
+### 2. Book management from reader menu (MEDIUM)
+
+**Files**: `EpubReaderMenuActivity.h`, `EpubReaderMenuActivity.cpp`, `EpubReaderActivity.cpp`
+
+- Added `ARCHIVE_BOOK`, `DELETE_BOOK`, `REINDEX_BOOK` to `MenuAction` enum
+- Added corresponding menu items between CLOSE_BOOK and DELETE_CACHE
+- Added handlers in `onReaderMenuConfirm`: each calls `BookManager::archiveBook/deleteBook/reindexBook` then `activityManager.goHome()`
+
+### 3. Silent next-chapter pre-indexing (MEDIUM)
+
+**Files**: `EpubReaderActivity.h`, `EpubReaderActivity.cpp`
+
+- Added `preIndexedNextSpine` field and `silentIndexNextChapterIfNeeded()` method
+- Triggers when user is on second-to-last or last page of a chapter
+- Creates section file for `currentSpineIndex + 1` in advance
+- Called after every page turn in `loop()`
+- ~35 lines of self-contained implementation
+
+### 4. Letterbox fill toggle in reader menu (LOW)
+
+**Files**: `EpubReaderMenuActivity.h`, `EpubReaderMenuActivity.cpp`, `EpubReaderActivity.cpp`
+
+- Added `LETTERBOX_FILL` to `MenuAction` enum
+- Added `bookCachePath` constructor parameter (with default `""` for backward compat)
+- Added per-book `pendingLetterboxFill`, `letterboxFillLabels`, `letterboxFillToIndex()`, `indexToLetterboxFill()`, `saveLetterboxFill()`
+- Cycles Default → Dithered → Solid → None → Default on Confirm
+- Renders current value on right edge of menu item
+- Loads/saves per-book setting via `BookSettings`
+- Updated call site in `EpubReaderActivity` to pass `epub->getCachePath()`
+
+## Audit False Positives (confirmed NOT gaps)
+
+- GfxRenderer kerning/ligatures/wrappedText — present on resync
+- HttpDownloader auth fallback — present with OPDS settings fallback
+- Lyra3CoversTheme — exists on resync
+- ActivityWithSubactivity → Activity migration — intentional upstream change
+- EndOfBookMenuActivity callbacks → setResult/finish — correctly migrated
+
+## Follow-up Items
+- None