Unable to set a transaction fee of <1 sat/vB when using "send"

When trying to use the "send" option in Jam, it only seems to accept transaction fee rates between 1.001 and 350 sats/vB, even when updating my bitcoin node config to allow <1 sat/vB transaction fees.

Start at the Jam "send" option and reproduce the issue with a transaction fee below 1 sat/vB while the Bitcoin node is configured to allow it. Trace where the fee range is rejected, then verify that valid sub-1 sat/vB values are accepted without breaking the existing range.

Written by the indexing model from the issue text.