Alright, so this is less pretty than I hoped for, but here it is:
select
agent.*,
case when exists(
select *
from msdb.dbo.sysjobsteps step
where agent.job_id=step.job_id
and step.step_id=2
and step.command like '%-Continuous%')
then 1
else 0
end as Continuous
from distribution.dbo.MSmerge_agents agent
Deduced from this script, which I found through desperate internet searches. This assumes case-insensitivity for string matches.
If anyone has a better/neater/prettier solution, I'll still award the answer to them.