docs/dev: add generated pipeline reference

Created by: bobheadxi

Commits the generated reference introduced in https://github.com/sourcegraph/sourcegraph/pull/30532 into the docsite. Closes https://github.com/sourcegraph/sourcegraph/issues/30203

I am placing this under dev/background-information/ci - I hope to consolidate CI docs in here some day, but that will require some redirects and link updates so I'll just let this be the only file for now.

We can expand this in the future with https://github.com/sourcegraph/sourcegraph/issues/28286 , for example, and tweak it for readability if helpful

Test plan

go generate ./enterprise/dev/ci
sg ci docs # see adjusted intro output
sg run docsite

Visit http://localhost:5080/dev/background-information/ci/reference