Sometimes the best way to answer a question is to just ask it out loud.
<meta name="author" content="{{ .Site.Author.name }}">
No “.Params” in the variable name. I figured this out by creating a partial with @natefinch's print statement:
$ vi layouts/partials/dumpdot.html
{{ printf "%#v" . }}
:wq
When I called {{ partial "dumpdot.html" .Site }}, I noticed that Author was at the top level. A quick update to call {{ partial "dumpdot.html" .Site.Author }} showed me what I was missing and I felt mighty humble.
I want to add that the live reload makes this quick and painless.