fix: placeholder cover text, indexing timing, TOC long-press, cache deletion UI

- Fix fp4 fixed-point misuse in PlaceholderCoverGenerator (advanceX is 12.4
  fixed-point, not pixels) causing only first letter of each word to render
- Remove duplicate silentIndexNextChapterIfNeeded() call from loop() that
  blocked UI before render, preventing the indexing indicator from showing
- Fix indexing icon Y position to align within the status bar
- Add ignoreNextConfirmRelease to EpubReaderChapterSelectionActivity so
  long-press confirm release doesn't immediately select the first TOC item
- Reload recent books after cache deletion in HomeActivity and clear stale
  ignoreNextConfirmRelease flag to fix "no open books" and double-press bugs

Made-with: Cursor

src/activities/reader/EpubReaderChapterSelectionActivity.h

@@ -12,6 +12,7 @@ class EpubReaderChapterSelectionActivity final : public Activity {
   ButtonNavigator buttonNavigator;
   int currentSpineIndex = 0;
   int selectorIndex = 0;
+  bool ignoreNextConfirmRelease = false;
 
   // Number of items that fit on a page, derived from logical screen height.
   // This adapts automatically when switching between portrait and landscape.
@@ -23,11 +24,12 @@ class EpubReaderChapterSelectionActivity final : public Activity {
  public:
   explicit EpubReaderChapterSelectionActivity(GfxRenderer& renderer, MappedInputManager& mappedInput,
                                               const std::shared_ptr<Epub>& epub, const std::string& epubPath,
-                                              const int currentSpineIndex)
+                                              const int currentSpineIndex, bool consumeFirstRelease = false)
       : Activity("EpubReaderChapterSelection", renderer, mappedInput),
         epub(epub),
         epubPath(epubPath),
-        currentSpineIndex(currentSpineIndex) {}
+        currentSpineIndex(currentSpineIndex),
+        ignoreNextConfirmRelease(consumeFirstRelease) {}
   void onEnter() override;
   void onExit() override;
   void loop() override;