feat: Integrate PR #857 dictionary intelligence and sub-activity refactor

Pull in the full feature update from PR #857 while preserving fork
advantages (HTML parsing, custom drawHints, PageForward/PageBack,
cache management, stardictCmp, /.dictionary/ paths).

- Add morphological stemming (getStemVariants), Levenshtein edit
  distance, and fuzzy matching (findSimilar) to Dictionary
- Create DictionarySuggestionsActivity for "Did you mean?" flow
- Add onDone callback to DictionaryDefinitionActivity for direct
  exit-to-reader via "Done" button
- Refactor DictionaryWordSelectActivity to ActivityWithSubactivity
  with cascading lookup (exact → stems → suggestions → not found),
  en-dash/em-dash splitting, and cross-page hyphenation
- Refactor LookedUpWordsActivity with reverse-chronological order,
  inline cascading lookup, UITheme-aware rendering, and sub-activities
- Simplify EpubReaderActivity LOOKUP/LOOKED_UP_WORDS handlers

Co-authored-by: Cursor <cursoragent@cursor.com>

src/activities/reader/LookedUpWordsActivity.h

@@ -13,12 +13,14 @@
 class LookedUpWordsActivity final : public ActivityWithSubactivity {
  public:
   explicit LookedUpWordsActivity(GfxRenderer& renderer, MappedInputManager& mappedInput, const std::string& cachePath,
-                                 const std::function<void()>& onBack,
-                                 const std::function<void(const std::string&)>& onSelectWord)
+                                 int readerFontId, uint8_t orientation, const std::function<void()>& onBack,
+                                 const std::function<void()>& onDone)
       : ActivityWithSubactivity("LookedUpWords", renderer, mappedInput),
         cachePath(cachePath),
+        readerFontId(readerFontId),
+        orientation(orientation),
         onBack(onBack),
-        onSelectWord(onSelectWord) {}
+        onDone(onDone) {}
 
   void onEnter() override;
   void onExit() override;
@@ -26,12 +28,16 @@ class LookedUpWordsActivity final : public ActivityWithSubactivity {
 
  private:
   std::string cachePath;
+  int readerFontId;
+  uint8_t orientation;
   const std::function<void()> onBack;
-  const std::function<void(const std::string&)> onSelectWord;
+  const std::function<void()> onDone;
 
   std::vector<std::string> words;
   int selectedIndex = 0;
   bool updateRequired = false;
+  bool pendingBackFromDef = false;
+  bool pendingExitToReader = false;
   ButtonNavigator buttonNavigator;
 
   // Delete confirmation state
@@ -42,6 +48,7 @@ class LookedUpWordsActivity final : public ActivityWithSubactivity {
   TaskHandle_t displayTaskHandle = nullptr;
   SemaphoreHandle_t renderingMutex = nullptr;
 
+  int getPageItems() const;
   void renderScreen();
   static void taskTrampoline(void* param);
   [[noreturn]] void displayTaskLoop();