_load() treated any OSError like corruption and returned an empty store. When pairing.json was transiently unreadable, an unapproved DM could deny the sender, generate a pairing code from the empty view, and overwrite the store without its approved senders.
Keep the existing JSONDecodeError reset behavior, but propagate OSError so mutations cannot persist unreadable state. Read-only checks fail closed without writing; mutating /pairing subcommands report temporary unavailability; and the DM pairing path skips one reply instead of crashing the handler.
This mirrors the refuse-to-overwrite strategy used by the cron and trigger stores.