fix(gcode): stricter gcode line number matching

[barthy-koeln]

Changes

The current G-CODE syntax is too loose on the "line number" instruction matching.

Example:

N1 M6
N2 SAVE_CONFIG

Rendered as:

<span class="hljs-symbol">N1</span> <span class="hljs-name">M6</span>
<span class="hljs-symbol">N1</span> SAVE_CO<span class="hljs-symbol">NFIG</span>

NFIG is not a line number instruction or symbol. My proposed fix is to strictly match the letter N, followed by one or more digits.

---

This does not resolve all issues, such as matching N\d+ that is NOT at the start of the line:

SKEW_PROFILE SAVE=GuteN8

Rendered as

SKEW_PROFILE SAVE=Gute<span class="hljs-symbol">N8</span>

I haven't found a straightforward and reliable specification or source listing exactly which optional characters are allowed before line numbers. Unfortunately, I currently don't have the time to dive deeper into ISO specs.

But I think that this a good minimal change that resolves some issues and hopefully doesn't cause others.

Checklist

• [x] Added markup tests
• [x] Updated the changelog at CHANGES.md

[barthy-koeln]

I suggest closing this in favor of #4040

[joshgoebel]

Closing per suggestion.