MEDYAN.fila_chem_positions
Tuple{MEDYAN.Context, MEDYAN.FilaIdx}
Return a view of the chemistry cylinder endpoint positions for the filament.
These are the raw positions used for chemistry calculations, at the boundaries between cylinders. Unlike fila_node_positions, the first and last positions are NOT adjusted for partial cylinders or tip extension. Use get_position(c, FilaTipIdx(...)) for the actual tip positions. This can be invalid after any mutations to context, so copy if needed.