document functions "under the hood"

**Describe the content issue**:
A clear and concise description of what the content issue is. Is there content missing or is there incorrect content?

- how secrets are resolved automatically
- where that snippet is
- prebaked cjs shim
- performance optimizations
- how bundling works

**URL page where content issue is**:

No source file, test, or page URL is named; begin by locating the snippets and entry points for secret resolution, the prebaked CJS shim, performance optimizations, and bundling. Done means documenting each listed under-the-hood topic on the relevant documentation page.

Written by the indexing model from the issue text.