feat: BookInfo button mapping, ManageBook integration, cover regen fix

- Fix BookInfo buttons: Left/Right front = scroll down/up, Confirm = no-op,
  side buttons retained. Separate Up/Down hints on btn3/btn4.
- Fallback load: try epub.load(true, true) when cache-only load fails,
  so Book Info works for unopened books.
- Add "Book Info" to ManageBook menu (BOOK_INFO action) with handlers in
  all 4 result sites (Home, Recent, FileBrowser, Reader).
- Fix HomeActivity cover regen: call generateCoverBmp(false) + validate
  with isValidThumbnailBmp before falling to placeholder, matching the
  reader's multi-tier fallback pipeline. Same for XTC branch.

Made-with: Cursor

chat-summaries/2026-03-09_02-30-summary.md

@@ -0,0 +1,51 @@
+# BookInfo Button Mapping, Fallback Load, ManageBook Integration, Cover Regen Fix
+
+**Date**: 2026-03-09  
+**Task**: Implement fixes 1-5 from the BookInfo Buttons and Load plan
+
+## Changes Made
+
+### BookInfoActivity.cpp — Fixes 1-3
+
+1. **Button mapping** (`loop()`): Removed `Confirm` as exit trigger. Added `Left` and `Right` front buttons as scroll-down/scroll-up handlers alongside existing side-button `Down`/`Up` and `PageForward`/`PageBack`.
+2. **Button hints** (`render()`): Updated `mapLabels` to show `STR_DIR_DOWN` on Left (btn3) and `STR_DIR_UP` on Right (btn4), with separate variables for each direction instead of a single combined hint.
+3. **Fallback load** (`onEnter()`): Changed `epub.load(false, true)` pattern to try `epub.load(true, true)` on failure, ensuring cache is built for books that were never opened. XTC branch already builds unconditionally via `xtc.load()`.
+
+### BookManageMenuActivity — Fix 4
+
+- Added `BOOK_INFO` to `Action` enum (first entry)
+- Added `STR_BOOK_INFO` menu item as first entry in `buildMenuItems()`
+- Handled `BOOK_INFO` in all 4 result sites:
+  - `HomeActivity::openManageMenu()` — launches `BookInfoActivity` via `startActivityForResult`
+  - `RecentBooksActivity::openManageMenu()` — same pattern
+  - `FileBrowserActivity::handleManageResult()` — same pattern
+  - `EpubReaderActivity` inline switch — same pattern
+- Added `BOOK_INFO` no-op case to `executeManageAction()` in Home/Recent to prevent compiler warnings
+
+### HomeActivity cover regeneration — Fix 5
+
+- After `generateThumbBmp()` fails or produces invalid BMP, now calls `generateCoverBmp(false)` to extract the full cover from the EPUB before retrying thumbnail generation
+- Added `Epub::isValidThumbnailBmp()` validation after each `generateThumbBmp()` call
+- Applied same pattern to XTC branch using `xtc.generateCoverBmp()` + validation
+- This aligns the HomeActivity pipeline with the EpubReaderActivity's multi-tier fallback approach
+
+## Files Changed
+
+- `src/activities/home/BookInfoActivity.cpp` — button mapping, hints, fallback load
+- `src/activities/home/BookManageMenuActivity.h` — BOOK_INFO enum entry
+- `src/activities/home/BookManageMenuActivity.cpp` — BOOK_INFO menu item
+- `src/activities/home/HomeActivity.cpp` — BOOK_INFO handler + cover regen fix
+- `src/activities/home/RecentBooksActivity.cpp` — BOOK_INFO handler
+- `src/activities/home/FileBrowserActivity.cpp` — BOOK_INFO handler
+- `src/activities/reader/EpubReaderActivity.cpp` — BOOK_INFO handler
+
+## Build Result
+
+Build succeeded — 0 errors, 0 code warnings. RAM: 30.3%, Flash: 95.7%.
+
+## Follow-up Items
+
+- Test on device: verify all 4 BookInfo entry points work (Home manage, Recent manage, FileBrowser manage, Reader manage)
+- Test cover regeneration after DELETE_CACHE from reader menu
+- Verify button mapping on BookInfo screen (Left=down, Right=up, side buttons=scroll)
+- Verify Book Info shows for books that have never been opened