WebTransport for parallel model weight streaming from CDN

[sauravpanda]

Context

WebTransport extends HTTP/3 with multiplexed streams over QUIC. Lower latency than WebSocket, supports multiple parallel streams.

Proposal

• Use WebTransport to stream model layers in parallel from CDN
• Multiple QUIC streams download different layer groups simultaneously
• Priority scheduling: download layers needed soonest first
• Combined with progressive inference (Progressive inference: start generating with partial model load #383): start generating while layers still downloading
• Graceful degradation to fetch() for browsers without WebTransport

Impact

• 2-4x faster model loading via parallel streams
• Reduced time-to-first-token on slow connections