exifr keeps a page-long cache of the options object it is handed, keyed by
that object itself, so a fresh literal per frame pinned a frame's worth of
tag sets (about thirty Sets) for as long as the tab lived: 3601 frames left
~16MB of heap behind, 9601 left ~50MB, and a roll of a hundred thousand
frames is what a tab cannot hold.
One options object per call site now, which is what that cache is for.
Measured on the deployed bundle: 3601 frames rest at 8MB, not 23MB.
scripts/ram-check.mjs reads a roll of many folders, queues folders behind
the reading in front of them and reports the heap left after a forced
collection, which is how those numbers were taken.
