Add visible configuration prompts

[PurpleSentinel]

Summary

• add concise swipe instructions to track, rest, and Launch Mode configuration screens
• keep the prompts visible after each value change
• place both instructions within the safe circular display area
• update the User Guide with the on-screen workflow
• correct black proportional-font rendering on the MicroPython framebuffer

Root cause

The configuration screens did not explain how to change or save values. During hardware validation, the new prompts and existing black labels were also found to be invisible because the font blitter used black as its transparency key. After palette mapping, this discarded black foreground glyphs along with transparent background pixels.

Impact

Configuration screens now show Swipe L/R to change and Swipe UP: save. Black labels render correctly throughout the firmware instead of disappearing.

Validation

• python -m unittest discover -s tests -v - 63 tests passed
• regression coverage confirms prompts persist on redraw and fit inside the round display
• regression coverage confirms black text does not use the transparent blit key
• deployed and rendered on the connected Waveshare RP2040-Touch-LCD-1.28
• captured the 115,200-byte production framebuffer and visually confirmed all labels and prompts