An update restores content that went missing

Updating an installed plugin used to fetch only the files whose content had changed since the last install. That is the right thing to do when nothing else moved — but if one of the plugin's nodes had disappeared from the mesh in the meantime, its file was unchanged, so the update skipped it and the node stayed gone. Every later update skipped it again, and each one reported success.

An update now checks the mesh before it fetches. Any file the plugin ships whose node is missing is re-fetched and written back, alongside the files that genuinely changed — so the ordinary "update the plugin" action repairs the gap instead of stepping over it.

Two smaller things travel with it:

• If the mesh cannot be read at that moment, the update says so and does not quietly proceed as if everything were present.
• If the source returns fewer files than the update asked for, that shortfall is now named instead of passing unnoticed.

The symptom this removes: a plugin whose views render empty, or whose node type will not compile, because source files the install record still lists are not actually there.