Legal: counsel review — ODbL share-alike boundary + topic copy strategy

[espi]

Needs counsel sign-off before commercial release built on the Marble data.

Two questions from 04-law-ip.md, Q4.1:

1. Validate the working reading: app experiences are ODbL "produced works" (attribution only); our overlay corrections to Marble records are potentially conveyable derivative-database content; our independent calibration data, kept structurally separate, is not.
2. Parent-facing topic copy: reuse Marble's description/evidence text (CC-BY-SA obligations, attribution UI) vs. rewrite in our own voice (clean, but ~1,590 topics of copywriting). Decide per surface.

Attribution notice should ship in the app footer regardless (text in vendor/os-taxonomy/README.md).