Fix stale cache launches, FNF runtime deps, and uninstall focus death (v0.1.20)

- Inject the user-level shared-libs dir into LD_LIBRARY_PATH for installed
  games so FNF finds libvlc.so.5 (idempotent, avoids duplicate entries)
- Reconcile cached installs against butlerd's live caves: normalize
  int/float ids, wait for butlerd when the cache claims installs, keep the
  cache when Fetch.Caves fails, and re-save the reconciled cache
- get_caves() returns null on RPC error (vs [] for genuinely nothing
  installed) so callers can tell a transient failure apart
- Patch freshly installed/updated items in place so the Play button launches
  the new binary immediately
- Drop and re-add items through the LibraryManager so the library menu
  re-renders after install/uninstall (core handler is a no-op upstream)
- Restore launch-page focus after uninstall by searching get_tree().root:
  get_tree().current_scene is null in OGPU, so the old fix silently no-oped
  and left the D-pad dead

plugin.json

@@ -1,7 +1,7 @@
 {
   "plugin.id": "itch",
   "plugin.name": "itch.io",
-  "plugin.version": "0.1.12",
+  "plugin.version": "0.1.20",
   "plugin.min-api-version": "1.1.0",
   "plugin.link": "https://forge.thergic.ar/jose/itchio-opengamepadui-plugin",
   "plugin.source": "https://forge.thergic.ar/jose/itchio-opengamepadui-plugin",