Feature request: Show Line Numbers and/or Show Cursor Position

[prupert]

Summary

Add a way to see line numbers and/or the cursor position in Nota.

Motivation

Line and column numbers are the standard way to reference a specific location in a text file.

Some of my use cases:

• Collaborating (or talking to myself or LLM's while working) on a document and pointing to a specific spot ("see line 142")
• Cross-referencing errors or feedback from external tools that report positions: nota-yay.md:56:7 beep bloop
• Navigating long documents, where line numbers are more precise than scrolling

Proposed solution

Two complementary options, ideally both:

• Passive: line number gutter. Optional gutter on the left margin showing line numbers, toggleable via top menu "View -> Show Line Numbers", perhaps alongside "View -> Show Markdown".
• Active: shows cursor position. Display something like "Ln X, Col Y" or "X:Y" in the bottom status area, alongside and in the same style as the existing optional Word Count, toggleable via top menu "View -> Show Cursor Position", perhaps alongside "View -> Show Word Count".

Either alone would be useful. Together they cover both "where I am looking" and "where am I now".