Clear cache on prewarm

lib/EpdFont/FontDecompressor.h

@@ -7,7 +7,7 @@
 class FontDecompressor {
  public:
   static constexpr uint16_t MAX_PAGE_GLYPHS = 512;
-  static constexpr uint8_t MAX_PAGE_SLOTS = 4;  // One per font style (R/B/I/BI)
+  static constexpr uint8_t MAX_PAGE_SLOTS = 8;  // Provide enough slots for heavily stylized HTML pages
 
   FontDecompressor() = default;
   ~FontDecompressor();

lib/GfxRenderer/FontCacheManager.cpp

@@ -24,6 +24,8 @@ void FontCacheManager::clearCache() {
 }
 
 void FontCacheManager::prewarmCache(int fontId, const char* utf8Text, uint8_t styleMask) {
+  clearCache();
+
   // SD card font prewarm path: prewarm all requested styles in one call
   auto sdIt = sdCardFonts_.find(fontId);
   if (sdIt != sdCardFonts_.end()) {