mod: adapt mod activities to #774 render() pattern

Migrate 5 mod Activity subclasses from old polling-based
display task pattern to the upstream render() super-class
pattern with freeRTOS notification:

- EpubReaderBookmarkSelectionActivity
- DictionaryWordSelectActivity
- DictionarySuggestionsActivity
- DictionaryDefinitionActivity
- LookedUpWordsActivity

Changes: remove own TaskHandle/SemaphoreHandle/updateRequired,
use requestUpdate() + render(RenderLock&&) override, fix
potential deadlocks around enterNewActivity() calls.

Also fix stale conflict marker in EpubReaderMenuActivity.h.

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

src/activities/reader/EpubReaderBookmarkSelectionActivity.h

@@ -1,8 +1,5 @@
 #pragma once
 #include <Epub.h>
-#include <freertos/FreeRTOS.h>
-#include <freertos/semphr.h>
-#include <freertos/task.h>
 
 #include <memory>
 #include <vector>
@@ -15,32 +12,19 @@ class EpubReaderBookmarkSelectionActivity final : public ActivityWithSubactivity
   std::shared_ptr<Epub> epub;
   std::vector<Bookmark> bookmarks;
   std::string cachePath;
-  TaskHandle_t displayTaskHandle = nullptr;
-  SemaphoreHandle_t renderingMutex = nullptr;
   ButtonNavigator buttonNavigator;
   int selectorIndex = 0;
-  bool updateRequired = false;
   bool deleteConfirmMode = false;
   bool ignoreNextConfirmRelease = false;
   int pendingDeleteIndex = 0;
   const std::function<void()> onGoBack;
   const std::function<void(int newSpineIndex, int newPage)> onSelectBookmark;
 
-  // Number of items that fit on a page, derived from logical screen height.
   int getPageItems() const;
-
   int getTotalItems() const;
-
-  // Build the prefix portion of a bookmark label (chapter + snippet, without page suffix)
   std::string getBookmarkPrefix(const Bookmark& bookmark) const;
-
-  // Build the page suffix (e.g. " - Page 5")
   static std::string getPageSuffix(const Bookmark& bookmark);
 
-  static void taskTrampoline(void* param);
-  [[noreturn]] void displayTaskLoop();
-  void renderScreen();
-
  public:
   explicit EpubReaderBookmarkSelectionActivity(GfxRenderer& renderer, MappedInputManager& mappedInput,
                                                const std::shared_ptr<Epub>& epub,
@@ -57,4 +41,5 @@ class EpubReaderBookmarkSelectionActivity final : public ActivityWithSubactivity
   void onEnter() override;
   void onExit() override;
   void loop() override;
+  void render(Activity::RenderLock&&) override;
 };