substrate-interface is intentionally not a direct dep (see pyproject.toml
note — it conflicts with the scalecodec namespace bittensor>=10 needs).
The runtime modules already import Keypair from bittensor_wallet first
and fall back; the e2e test was the one place still hard-importing
substrateinterface, which broke CI test collection.

Same Keypair class — bittensor_wallet re-exports it. 412 tests pass.