RFD 1098 details: the deploy modes, the forbidden variables, and local verify

Compacted. This RFD is abandoned, so its working-out was removed to keep the live corpus small. 487 words are in git history and nothing was lost.

git show ac8201e2df493305313466c3764ce2cc2d88bdec:rfd/1098-public-deploy/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.