[…] I deleted the "remove trailing whitespace" item from the Text bundle.

How can I recover the item?

To revert the (entire) Text bundle to its default state:

rm -rf "$HOME/Library/Application Support/Avian/Bundles/Text.tmbundle"

I gave that a try, but I still don't see the command in the Text bundle menu. I did some poking around and I don't see "Remove Trailing Spaces in Document" in $HOME/Library/Application Support/TextMate/Managed/Bundles/Text.tmbundle/Commands.

I even deleted the directory, deleted TextMate.app, and did a fresh install. I still don't see the command in the TextMate tree.