Arising from the discussion on the morning of June 7th:

Please add a remote API for a combined display-zoom-pan operation for Firefly, that would make it possible to bring up an image with both an initial center point and initial zoom level specified.

This will make it possible to optimize the performance of Firefly in situations in which it is desired to examine a small part of an image around a point of interest, without resorting to the use of a cutout service.  In some applications it is preferable to still have the whole image in principle available for panning and/or zooming out.

Based on discussions of the features already available, it may be reasonable to structure this API so that it provides the option of placing a Firefly "marker" at the selected center point.

Bonus feature (which may need to be deferred to another ticket): ensure that the "reset" toolbar button (↪️, "restore to the defaults") returns the display to the API-chosen starting point and zoom level, rather than to something like "fit to window" or "1:1".  I think this is the more natural expectation for users.  (I don't know if this would already just work or require extra effort.)

The new API would need to be exposed in firefly_client and the implementation in display_firefly modified to ensure that zoom and pan commands executed before mtv() are properly recorded and applied once mtv() is called.