root -> rooted_tree
depth_cach -> walk
smal refactor
comment
remove form for header_section
remove seen_at from header section
header_section: champ -> header_section
champ_subree: remove if not
remove root_depth use header_section_level_value instead
remove unused include
remove ChampTreeComponent
rename ChampsSubtreeComponent to SectionComponent
use TreeableConcern only in section component
remove fields_for_champ_component
champs -> tail
add split_section_champ helper
refactor(editable_champ::header_section): keep same interface everywhere
fix(repetition): add spec for SectionComponent on repetitions
