meld:master commits

The ability to start a new comparison on a subfolder was mistakenly removed when fixing an inconsistency with creating a comparison where one of the files was missing.

data: Rename appdata to metainfo See merge request !140

The latter is preferred nowadays and is used by other GNOME projects. Also change the AppStream component type to "desktop-application" instead of a deprecated "desktop" one

This is prompted by a Python 3.14 incompatibility issue in pytest; the other updates are just to keep things current.

The action gutter normally only recalculates the pointer chunk on motion/enter/leave events, but we need to also do this when the actual underlying chunk set changes. This is normally an invisible issue due to small cursor movements, etc. but a double-click or very controlled clicks without cursor movement easily reproduce the problem. Technically this is not an ideal solution. We *should* recalculate the current pointer chunk when the chunks change instead of nulling it out, but that would require us to keep the pointer coordinates and do a few other things that I don't really want to do for the GTK 3 branch at this point.