Plugin pages show their overview, and installations repair themselves

Opening a plugin you had not purchased could show a raw permission error above the page instead of the plugin's own cover. Being asked to buy something is a normal state, not a fault, so the page now simply shows what it is offering.

Installations are also more robust about the plugins they ship with. Previously a deployment whose plugin configuration was wrong on its very first start would come up looking healthy but with nothing installed, and correcting the configuration afterwards had no effect — the only route back was a rebuild from scratch. An installation now completes any plugin it has not yet delivered the next time it starts, while leaving anything an administrator removed on purpose alone.