Peer-first model fetch

# config.toml
[iroh]
enable = true

# or
tenzro-node --role validator --iroh.enable

HfArtifactDownloader consults connected iroh peers via a PeerHint before reaching Hugging Face. If a peer has the BLAKE3 already, the transfer is end-to-end-verified over QUIC; if not, HF is the fallback.

tenzro model download timesfm-2.5 --prefer-peers

On successful HF fetch the downloader publishes the blob into the local iroh-blobs store. Subsequent fetchers on this or any peer node skip the HF round trip — the network warms itself.

Any artifact resolved this way is reachable through the unified scheme — tenzro://blob/<blake3-hex> — regardless of which path supplied the bytes.