RFD 1050 details: the phases, the gravity rule, the metric gate, blockers

Compacted. This RFD is abandoned, so its working-out was removed to keep the live corpus small. 221 words are in git history and nothing was lost.

git show ac8201e2df493305313466c3764ce2cc2d88bdec:rfd/1050-lingbot-map-environment-scan/DETAILS.md

The README beside this file is whole. It carries the state, the decision and the retraction, which is what a reader needs to know a road is closed and why.