Directory tree significantly restructured.

All top-level scripts excluding ={main} now reside under ={!!-seed}, an
ignorable suboverlay (i.e., a subdirectory explicitly ignored by ={compile} for
purposes of digest compilation). All unconditionally compiled top-level
suboverlays have been renamed in favour of "organic" nomenclature (e.g., from
={00-start} to ={00-soil}), as mute protest against the patent sterility
promulgated by most codebases. A nefarious retinue of other changes accompany.