Improve pre warm caching

lib/GfxRenderer/GfxRenderer.h

@@ -115,6 +115,10 @@ class GfxRenderer {
   // (which holds a const GfxRenderer&) before measuring word widths. Safe to call on
   // non-SD fonts (no-op).
   void ensureSdCardFontReady(int fontId, const char* utf8Text) const;
+  // Clear the cumulative SD card font metadata cache built up by repeated
+  // ensureSdCardFontReady() calls. Call between sections to bound the cumulative
+  // codepoint set growth across pagination. Safe to call when no SD font is active.
+  void clearSdCardFontAccumulation() const;
 
   // Orientation control (affects logical width/height and coordinate transforms)
   void setOrientation(const Orientation o) { orientation.store(static_cast<int>(o), std::memory_order_relaxed); }