Prevent accidental overresearching / inspiration waste

Next to the currently researching tech and civic in the upper left, add a checkbox option that -- if enabled -- prevents ending a turn that will research past 50% (60% for China)

Start by locating the Lua UI entry point that renders the current researching tech and civic in the upper-left area, then trace how ending a turn advances research. Confirm how the China threshold differs before implementing the checkbox behavior. Done means the option is visible there and enabled players cannot end a turn that would research past the applicable threshold.

Written by the indexing model from the issue text.