Demo UI Fixes

[PolyCement]

Fixes for various UI issues as listed in #159. Currently covers:

• [x] copy link button text should probably have a shorter timer on switching back, i thought it'd broken
• [x] "click to show flows" still appears during a comparison, but clicking disables the comparison
• [x] click to show flows tip vanishes while a region is selected (that might actually be my fault lol)
• [x] selected region in flow view doesn't draw unless flows are toggled off...?
• [x] scenario & year seem to default to first in list but don't initially set their displayed values

Also partially covers:

• [ ] could probably use on-screen instructions for map controls (click, ctrl+click, etc)

[cmcaine]

Thank you!