The shim expanded NIP-06 index N into role=main + role_path=m/44'/1237'/N'/0/0
client-side. It is removed — callers must now use
nostr_signer_nsigner_set_role_path explicitly.
Added nostr_signer_nsigner_set_derive_index for the derive verb's algorithm
index (previously set as a side effect of the shim).
Updated NSIGNER_INTEGRATION.md and plan docs to reflect the removal.
Tests: 8/8 pass.