Hover: show the message notes and the counterexample #188

The hover shows only the headline. The study's baseline condition has no panel, so the hover is the one surface both conditions share. Today it has no counterexample (timeout == -1 in A2_04, failures.size() == 0 in A2_10) and none of the message's notes (the where … means … gloss, and the planned From line).

Proposal

The hover shows the headline, then the message notes, then the counterexample (LJDiagnosticsHandler). The hints stay out of the hover: they are collapsed in the panel by design.