> I am thinking that at least the frozen-in-stone nav bar might
> be thawed, that a simple content insertion mechism for gallery
> items might be possible, that the RSS commit feed might be better
> integrated, or that the users manual might be auto-generated
> from some marked-up text.

Sounds more like a job for Ruwiki. 
http://rubyforge.org/projects/ruwiki/

The latest tarball there is release 0.7 which is a bit dated now.

Ruwiki is very extensible, supports definition of new markup and
pluggable storage backends.  (you can code a database storage plugin
very quickly)

Austin Ziegler has reported he's about to release 0.9 soon, and it
seems like it's well worth the wait.
I can't access his website right now, it's probably under maintenance.
Perhaps you can have a look at
http://www.halostatue.ca/blog/index.cgi/Tech/Ruby/Ruwiki
later, and see if it works.

best,
                   vruz