Show running G-code source line during job playback

[sfmissionmark]

Summary

• Track 1-based source line numbers on each parsed G-code segment
• Display Line X / Y in the viewer progress strip while a job is running or held
• Add a Code toggle in the G-code viewer toolbar with a scrollable source text panel
• Highlight and auto-scroll the current line in the text panel during Run/Hold
• Resolve the running line from toolpath position (with segment fraction interpolation) instead of SD byte-read progress, which reflects parser buffer position ahead of execution
• Parse FluidNC |Ln:N| from status reports when use_line_numbers is enabled and map N-words to source lines
• Store loaded G-code source text in the G-code store for the text panel

Test plan

• Load a G-code file in the viewer and confirm Code shows the full source with line numbers
• Start a job from SD and confirm Line X / Y appears above the progress bar during Run/Hold
• With Code open, confirm the highlighted line tracks the job and auto-scrolls
• Verify line numbers advance smoothly during cuts (not jumping in large SD-percent blocks)
• Confirm the display clears when the job stops or completes
• Test with a file that has comments/blank lines to verify line count includes full source
• Optional: enable use_line_numbers: true in FluidNC and N-words in G-code for Ln: reporting

[sfmissionmark]

This is actually not smoothly reporting the correct line number I think its jumping in buffer lengths or something. Taking this request back for testing.