- replace `rw vault ssh` calls with `rwagent.Client` in PrepareNodeKeys,
LoadAgentKeys, EnsureVaultEntry, ResolveVaultPublicKey
- add vaultClient interface, newClient func, and wrapAgentError for
testability and improved error messages
- prefer pre-built systemd dir in installNamespaceTemplates
- Deleted redeploy.sh, which handled redeployment to nodes in devnet/testnet environments.
- Removed upgrade-nodes.sh, responsible for rolling upgrades of nodes.
- Eliminated upload-source-fanout.sh, which uploaded source archives to nodes in parallel.
- Removed upload-source.sh, used for uploading and extracting source archives to VPS nodes.