Enhance snippet navigation and cursor tracking functionality

[nguyenanhduc09]

Introduce per-slot cursor tracking and interactive navigation for saved snippets: next/previous character, word, and line commands with localized names for special characters. Add helper functions for word/line parsing and a small _get_char_name utility; import re for parsing. Track current selected memory slot and initialize cursors when a slot is opened. Expand gesture mappings to include navigation shortcuts and many additional memory slots (minus/equals, numpad keys, backspace/numpadPlus/numpadMinus), and wire gestures for next/prev char/word/line. Also set current_slot_key to None when an empty slot is accessed.

[thgcode]

Hello!
Thank you for the contribution!
I have a question, I don't know your specific use case, but would it be easier to instead of having the implement the cursor code ourselves, the addon would display a browseable message with the snippet contents, so you could navigate by character, words or lines, and even also copy some specific parts you need? So the navigation code if there is a bug, can be fixed on the review cursor code itself and not on ours.