Whether to indicate "job sharing" option in application
Difficult question. Here are my thoughts, too long for a comment.
The fact that the university explicitly supports job sharing suggests that asking about it in your particular case would make sense.
It is possible that the explicit support is just pro forma. Can you find out whether there are any couples presently sharing a job? Do you have any contacts at the school to ask informally?
In your response to  @Buffy 's comment, you say you'd be OK if just one of you gets the job. Then I'd concur in waiting.
Speaking personally from my experience on hiring committees, I would appreciate knowing this information early, particularly the fact that one job would be acceptable even if two were preferable. For me it would strengthen the application(s).