v0.6.3 - restore the Mods page

If the Mods page was empty in v0.6.2, this release is the fix.

What was wrong

v0.6.2 put the mod catalog in one directory and then looked for it in another,
so the Mods page came up with nothing in it — no error, no warning, just an
empty list. Both the adaptive widescreen and MSU-1 packages were in the archive
the whole time; the game simply never read that folder.

This was introduced in v0.6.2 and affects the Windows build only.

Fixed

The catalog location now comes from one definition in the engine instead of
being spelled out separately by the build and the game, so the two cannot drift
apart again. Verified on a clean extract: both packages are present and the game
reads them from the directory they actually ship in.

Adaptive widescreen and MSU-1 are both on the Mods page, off by default.

Linux

The v0.6.1 AppImage was never affected and remains current. One thing worth
knowing about it: it copies its mod catalog next to the .AppImage file on
launch, and skips that silently if the containing folder is not writable. If
your Mods page is empty on Linux, move the .AppImage somewhere you can write
to and relaunch.