## Summary
First of several changes to decouple and clean up SD card fonts
integration. This change eliminates SdCardFontGlobals.h:
- Simply declare the `extern SdCardFontSystem sdFontSystem` in
SdCardFontSystem.h.
- `ActivityManager::goToReader` should not care about loading SD card
fonts. Instead do the same work in `ReaderActivity::onEnter`, after the
previous activity has exited and after ReaderActivity has validated the
file path.
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### AI Usage
While CrossPoint doesn't have restrictions on AI tools in contributing,
please be transparent about their usage as it
helps set the right context for reviewers.
Did you use AI tools to help write this code? _**NO**_
Zach Nelson
30b14f2ecf