Curseforge Sync

Fixes a bug that could leave two versions of the same mod in mods/ after a pack update, which prevents a Forge server from starting.

The problem. Installs were decided from the filesystem, but removals were decided only from config/curseforgesync-state.json. If that record was missing or incomplete, the new version of a mod was downloaded while the old one stayed behind. The most likely way to hit this was the very first sync on a server whose mods were already installed some other way — a server built from the pack by hand or by the CurseForge launcher. Nothing in the state file claimed responsibility for those jars, so when the pack updated a mod, its old copy was left in place.

The fix.

• After installing, both tracked and strict mode now sweep mods/ for older copies of the mods just installed
• Stale copies are identified by reading mod IDs out of the jars themselves, so this works even when the state file is missing, deleted, or was never written
• Jars that declare no mod are never matched, and protectedFiles still wins, so a build you placed by hand on purpose survives

If you were affected, just update and restart — the next sync cleans up the duplicates on its own. There is no need to clear the mods folder.

Mods that the pack dropped entirely are still left alone in tracked mode when there is no state file to identify them, since there is no way to tell them apart from jars you added yourself. They are harmless, unlike duplicates. Use strict mode if you want the mods folder mirrored exactly.