Fix Phriction document linking in mail bodies

Summary:
Fixes T10840. When rendering mail, this rule wasn't falling through in quite the right way.

Also adjust where the rules are for this so the special styles show up in Maniphest, etc.

Test Plan:
Made this comment:

Which produced this HTML:

...and sent this mail:

Reviewers: hach-que, chad

Reviewed By: chad

Maniphest Tasks: T10840

Differential Revision: https://secure.phabricator.com/D15767