(21881) Adds explantory text and fixes for YARD

From Nick Fagerlund:

Add explanatory text; modify the manifest to not throw an error. Add
node definitions.

Rename files (and any references to them).

Use indented code blocks instead of fenced ones

Our docs toolchain can't handle fenced code blocks yet, and we're going to need
to put this content in multiple places, so it must use least-common-denominator
markdown syntax.

Anchor links are not reliable in YARD

...so we should avoid them and describe anchor positions with English.