fix(m): correct shortlink resolution escaping
Previously we were escaping shortlinks before resolving them (and
in-fact doing that twice!). That's wrong, we should instead be escaping
the parameter for our default links but not escaping the resolved
shortlinks (as for direct they are replaced entirely with created
shortlinks and for regex the character set can be very restricted for
matches).
Escaping as we were prevented links like `a/b` working