Locking every tab but Tasks is right for install/restart/backup: those jump
to the task log, so Tasks is the one tab you need. A tool run deliberately
stays where it was launched and brings its result back to Tools — greying
Tools out stranded the user on a tab they could no longer return to.
disableTabs() now takes the tab to leave alone, chosen per task type by
keepTabFor(). Same rule on the page-load path, which also stops yanking a
reload mid-tool-run over to the task log.
63b3af4cfc