KeeperFX Linux Alpha 1.4.0.5322 — creature-list crash guard

Engine hardening release.

Fixes a crash when advancing between campaign levels caused by creature-list corruption (a list link pointing at a non-creature — symptom: a creature resting away from its lair, and "Jump to invalid creature N detected" in the log, then an abort). The engine now validates each creature in a list before using it across the ~18 walks that previously lacked that check: on a bad link it logs rich diagnostics and safely skips instead of aborting, so the game keeps playing. Purely additive guards, no gameplay change on healthy games.

This is a genuine engine bug present upstream too; the added logging is the path to a permanent root-cause fix if it recurs. Also includes everything from 5321 (in-launcher Workshop browser + Installed manager + single-instance lock).

Full notes: see CHANGELOG.md.