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/DictionarySuggestionsActivity.cpp

@@ -0,0 +1,141 @@
+#include "DictionarySuggestionsActivity.h"
+
+#include <GfxRenderer.h>
+
+#include "DictionaryDefinitionActivity.h"
+#include "MappedInputManager.h"
+#include "components/UITheme.h"
+#include "fontIds.h"
+#include "util/Dictionary.h"
+
+void DictionarySuggestionsActivity::taskTrampoline(void* param) {
+  auto* self = static_cast<DictionarySuggestionsActivity*>(param);
+  self->displayTaskLoop();
+}
+
+void DictionarySuggestionsActivity::displayTaskLoop() {
+  while (true) {
+    if (updateRequired && !subActivity) {
+      updateRequired = false;
+      xSemaphoreTake(renderingMutex, portMAX_DELAY);
+      renderScreen();
+      xSemaphoreGive(renderingMutex);
+    }
+    vTaskDelay(10 / portTICK_PERIOD_MS);
+  }
+}
+
+void DictionarySuggestionsActivity::onEnter() {
+  ActivityWithSubactivity::onEnter();
+  renderingMutex = xSemaphoreCreateMutex();
+  updateRequired = true;
+  xTaskCreate(&DictionarySuggestionsActivity::taskTrampoline, "DictSugTask", 4096, this, 1, &displayTaskHandle);
+}
+
+void DictionarySuggestionsActivity::onExit() {
+  ActivityWithSubactivity::onExit();
+  xSemaphoreTake(renderingMutex, portMAX_DELAY);
+  if (displayTaskHandle) {
+    vTaskDelete(displayTaskHandle);
+    displayTaskHandle = nullptr;
+  }
+  vSemaphoreDelete(renderingMutex);
+  renderingMutex = nullptr;
+}
+
+void DictionarySuggestionsActivity::loop() {
+  if (subActivity) {
+    subActivity->loop();
+    if (pendingBackFromDef) {
+      pendingBackFromDef = false;
+      exitActivity();
+      updateRequired = true;
+    }
+    if (pendingExitToReader) {
+      pendingExitToReader = false;
+      exitActivity();
+      onDone();
+    }
+    return;
+  }
+
+  if (suggestions.empty()) {
+    if (mappedInput.wasReleased(MappedInputManager::Button::Back)) {
+      onBack();
+    }
+    return;
+  }
+
+  buttonNavigator.onNext([this] {
+    selectedIndex = ButtonNavigator::nextIndex(selectedIndex, static_cast<int>(suggestions.size()));
+    updateRequired = true;
+  });
+
+  buttonNavigator.onPrevious([this] {
+    selectedIndex = ButtonNavigator::previousIndex(selectedIndex, static_cast<int>(suggestions.size()));
+    updateRequired = true;
+  });
+
+  if (mappedInput.wasReleased(MappedInputManager::Button::Confirm)) {
+    const std::string& selected = suggestions[selectedIndex];
+    std::string definition = Dictionary::lookup(selected);
+
+    if (definition.empty()) {
+      GUI.drawPopup(renderer, "Not found");
+      renderer.displayBuffer(HalDisplay::FAST_REFRESH);
+      vTaskDelay(1000 / portTICK_PERIOD_MS);
+      updateRequired = true;
+      return;
+    }
+
+    enterNewActivity(new DictionaryDefinitionActivity(
+        renderer, mappedInput, selected, definition, readerFontId, orientation,
+        [this]() { pendingBackFromDef = true; }, [this]() { pendingExitToReader = true; }));
+    return;
+  }
+
+  if (mappedInput.wasReleased(MappedInputManager::Button::Back)) {
+    onBack();
+    return;
+  }
+}
+
+void DictionarySuggestionsActivity::renderScreen() {
+  renderer.clearScreen();
+
+  const auto orient = renderer.getOrientation();
+  const auto metrics = UITheme::getInstance().getMetrics();
+  const bool isLandscapeCw = orient == GfxRenderer::Orientation::LandscapeClockwise;
+  const bool isLandscapeCcw = orient == GfxRenderer::Orientation::LandscapeCounterClockwise;
+  const bool isInverted = orient == GfxRenderer::Orientation::PortraitInverted;
+  const int hintGutterWidth = (isLandscapeCw || isLandscapeCcw) ? metrics.sideButtonHintsWidth : 0;
+  const int hintGutterHeight = isInverted ? (metrics.buttonHintsHeight + metrics.verticalSpacing) : 0;
+  const int contentX = isLandscapeCw ? hintGutterWidth : 0;
+  const int leftPadding = contentX + metrics.contentSidePadding;
+  const int pageWidth = renderer.getScreenWidth();
+  const int pageHeight = renderer.getScreenHeight();
+
+  // Header
+  GUI.drawHeader(
+      renderer,
+      Rect{contentX, hintGutterHeight + metrics.topPadding, pageWidth - hintGutterWidth, metrics.headerHeight},
+      "Did you mean?");
+
+  // Subtitle: the original word (manual, below header)
+  const int subtitleY = hintGutterHeight + metrics.topPadding + metrics.headerHeight + 5;
+  std::string subtitle = "\"" + originalWord + "\" not found";
+  renderer.drawText(SMALL_FONT_ID, leftPadding, subtitleY, subtitle.c_str());
+
+  // Suggestion list
+  const int listTop = subtitleY + 25;
+  const int listHeight = pageHeight - listTop - metrics.buttonHintsHeight - metrics.verticalSpacing;
+  GUI.drawList(
+      renderer, Rect{contentX, listTop, pageWidth - hintGutterWidth, listHeight}, suggestions.size(), selectedIndex,
+      [this](int index) { return suggestions[index]; }, nullptr, nullptr, nullptr);
+
+  // Button hints
+  const auto labels = mappedInput.mapLabels("\xC2\xAB Back", "Select", "Up", "Down");
+  GUI.drawButtonHints(renderer, labels.btn1, labels.btn2, labels.btn3, labels.btn4);
+
+  renderer.displayBuffer(HalDisplay::FAST_REFRESH);
+}