Show Me What This Is (SMWTI)

- Everything that is a setting now lives in the loader's own config. The choices for the settings other mods add, and the list of blocks and entities you hid, moved from `config/smwti-options.json` and `config/smwti-hidden.json` to `config/smwti-options.toml` (Forge and NeoForge config, with comments). Their number is not known when the loader builds the config, so each choice is one `"namespace:path=value"` line in a list.
- Migration: the first time `smwti-options.toml` does not exist and `smwti-options.json` does, the old values are imported exactly (renamed keys do not exist, every release wrote the same format; unknown ids are kept). The new file is written and read back first; then `smwti-options.json` is moved to `smwti-options.json.back` (a first line says where and why it migrated, then the exact original bytes; `.back2`, `.back3` if one exists, never overwritten) and the original is removed only after the backup is checked. A broken or partly readable file stays where it is with no backup: the readable values are imported, the rest use their defaults, and the log says why. `smwti-hidden.json` is read once and never changed. `smwti-client.toml` is unchanged.
- No setting or screen was added or changed.