Christian Nennemann
9fa3873bd7
Establishes the foundational transport layer for noiseml: - Noise_XX_25519_ChaChaPoly_BLAKE2s handshake (initiator + responder) via `snow`; mutual authentication of static X25519 keys guaranteed before any application data flows. - Length-prefixed frame codec (4-byte LE u32, max 65 535 B per Noise spec) implemented as a Tokio Encoder/Decoder pair. - Cap'n Proto Envelope schema with MsgType enum (Ping, Pong, and future MLS message types defined but not yet dispatched). - Server: TCP listener, one Tokio task per connection, Ping→Pong handler, fresh X25519 keypair logged at startup. - Client: `ping` subcommand — handshake, send Ping, receive Pong, print RTT, exit 0. - Integration tests: bidirectional Ping/Pong with mutual-auth verification; server keypair reuse across sequential connections. - Docker multi-stage build (rust:bookworm → debian:bookworm-slim, non-root) and docker-compose with TCP healthcheck. No MLS group state, no AS/DS, no persistence — out of scope for M1.