fix(jetbrains): measure the failure card text at its painted width

SessionLayout sizes MessageErrorView and then reads its preferred size, but the
wrapper's BorderLayout asked the text area for a preferred size without passing that
width down. A wrapping JBTextArea answered with one unwrapped line, so a long provider
error was clipped to a single-line slot.

Measure at the available width the way the transcript's other text rows already do.
Dropping the caret reset with it: there is no scroll pane around this area, so its only
effect was to let a new failure card yank the transcript scroll to itself.