Where are the docc files for the standard library?

when you visit the standard library docs, there are custom topics such as:

Creating a Binary Integer

Converting Integers

Converting Floating-Point Values

Converting with No Loss of Precision

Performing Calculations

where are the DocC files that specify these headings stored?

Symbol reference docs for the standard library come from the source repo, but the topic structure and some of the other content comes from the Apple Developer site.

Also note that the standard library has not yet migrated to Swift-DocC as the base tooling for generating the docs, but that is indeed a goal.