Preserve caller OmniAuth options

[OskarEichler]

Summary

• duplicate the OmniAuth argument list and its trailing options hash before extracting Devise-only configuration
• preserve :strategy_class in the caller's hash
• accept frozen provider options while still omitting :strategy_class from middleware arguments

Devise::OmniAuth::Config currently deletes :strategy_class directly from the supplied hash. This mutates reusable initializer configuration and raises FrozenError when that configuration is frozen.

Verification

• baseline mutable options lose :strategy_class
• baseline frozen options raise FrozenError
• fixed main and cumulative 5.0.4 consumer preserve the caller hash, resolve the requested strategy class, and expose middleware args without the Devise-only key
• focused OmniAuth config suite: 8 runs, 8 assertions, 0 failures
• full upstream and consumer Active Record suites: 878 runs, 2,470 assertions, 0 failures
• Ruby syntax check passes

No public option names or middleware arguments change. No test files were changed. Prepared with Codex assistance.