Fix beat divisor control selecting invalid divisors on drag end
* Use slider bar and slider marker coordinates in manual tests instead of hard-coded offsets. * Reword test steps slightly for greater clarity.
Update loader animation
* Use [Cached] injection instead of modifying beatmaps read from store. * Add assertion steps verifying the presence of mapper name (or lack thereof).
Forgot that if a PM channel was the last tab, it hid itself upon selecting due to changing its width, which made the last-visible-selected assert fail. Made this particular test only use non-PM channels.