Finalize SSD1677 four-mode refresh handling

[ainyan03]

Summary

• stabilize the SSD1677 four-mode refresh behavior
• use absolute Mode 1 waveforms for Quality and Text
• use state-tracked Mode 2 updates for Fast and Fastest
• preserve grayscale ordering across repeated updates, mode roundtrips, ping-pong parity, and sleep or power-save transitions
• keep LUT tuning helpers out of the public panel API

Hardware validation

Observed on PaperMono:

• Quality: 3465 ms
• Text: 585 ms
• Fast: 361 ms, with 279 ms observed on the second consecutive update
• Fastest: 97 ms
• mode roundtrip regression passed
• odd and even Mode 2 parity regression passed
• 50-repeat Fast stress test remained stable through the 60-second observation

CI

• Arduino Build: https://github.com/ainyan03/M5GFX/actions/runs/30258655621
• ESP-IDF Build: https://github.com/ainyan03/M5GFX/actions/runs/30258654899

Both workflows passed for commit 0c4b8fe.