First-system indent (for a title) is a real convention but should NOT be enforced in Gradus's current design

Traditionally, the first system of a piece is indented from the left margin to leave visual room for the title/composer credit printed above the staff.

Gould, Behind Bars (first-system indent convention); Ross, The Art of Music Engraving (same).

This rule can be decided from pitches, durations and voices — no layout required. A validator can check it before anything is drawn.