Tyre/Dudley/Araminta design round with Troblum adversarial critique and
completeness audit folded in (9-agent pass). Recommends: generalize the
district_window carrier with serde-default granularity + min-wavelength
params (no sixth demux shape); quarter rung as full reclassification at
512m; derive_at_metres extraction from derive_district's interior as the
keystone step; planetary rung as progressive capped-density tiling.
Carries measured-vs-estimated cost discipline and six explicit risks.
Decisions reserved for Jeroen: the D-226(d) floor question (stop at
quarter recommended), the planetary wire carrier, and the planetary-seam
interaction ruling.