sync docs from master after the 4.4.1 docs pass
publish the docs to the wiki, generated from docs/ Nineteen feature and operations docs, plus a configuration reference and an HTTP surface page written for someone building a consumer, plus a generated index and sidebar. Generated by scripts/wiki-sync.sh, so docs/ stays the source and this is output: do not hand edit a page other than Home or a release page. Seven docs are withheld by docs/.wikiignore. Four name a live deployment, an incident, or a design argument still open. Three are publishable after one edit each to remove a clause about the project's own playground.