Add support for ReFT

[RonanKMcGovern]

🚀 The feature, motivation and pitch

Motivation is to allow ReFT representations to be applied on the fly during inference, which can be done in a batchwise manner.

this is much faster than applying LoRAs

Alternatives

LoRA is too slow as it requires adapter weights to be added, which increases the number of operations.

Additional context

See https://github.com/stanfordnlp/pyreft/issues/63

[chris-aeviator]

as a user of pyreft I want to highlight the need for selecting subspaces into a hypothetical PyreftRequest (see https://github.com/stanfordnlp/pyreft/issues/63#issuecomment-2073233538)

[jvlinsta]

Any traction on this?

[github-actions[bot]]

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