migrate to using keypear derivation

[Nuhvi]

• Update NS to use standard of hypercore namespace generation

crypto_generichash(out=NS, input=Buffer.from([0]), ns=Buffer.from('slashtags'))

• Merge keychain branch to enable hyperdrive derivation with keychain

  • hash scalar before using as a tweak

• Use device tweaks and figure out the UX around that

  • Show root URL to user?
  • maybe slash:<root key>:<tweak> ??