feat: M3 seed — the lumen/1 native protocol: QUIC control plane + reference client (Phase 5)

The first end-to-end run of lumen's own protocol, past the GameStream compatibility layer.

- lumen-core/src/quic.rs (behind the `quic` feature): the lumen/1 handshake — Hello/Welcome/
  Start as length-prefixed LE binary on one QUIC bi-stream. Welcome carries the COMPLETE
  data-plane Config: mode, FEC scheme incl. GF(2^16) Leopard (inexpressible in GameStream),
  shard sizing, AES-GCM key + per-direction salt, data UDP port. Plus quinn endpoint helpers
  (self-signed server; accepts-any client — pinning lands with the trust model) and framed
  async IO. Round-trip unit-tested.
- lumen-host m3-host: serves one lumen/1 session — QUIC handshake, then a NATIVE thread
  (no async on the frame path — design invariant) streams deterministic 64KB test frames
  through the hardened M1 Session over UdpTransport.
- lumen-client-rs: from scaffold to working reference client — connects, negotiates, brings
  up the client Session over UDP, reassembles + FEC-recovers + byte-verifies every frame.

VALIDATED END-TO-END on localhost: 300/300 frames verified, 0 mismatches, through
QUIC-negotiated GF(2^16) FEC + AES-GCM over real UDP sockets. M4 (decode+present) builds on
this exact client skeleton.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/lumen-core/Cargo.toml

@@ -19,7 +19,7 @@ crate-type = ["lib", "cdylib", "staticlib"]
 default = []
 # Control-plane QUIC (pairing, config, reverse audio). tokio is permitted ONLY here,
 # never on the per-frame hot path. Off by default so the core stays runtime-free.
-quic = ["dep:quinn", "dep:tokio"]
+quic = ["dep:quinn", "dep:tokio", "dep:rustls", "dep:rcgen"]
 
 [dependencies]
 reed-solomon-simd = "3.1"      # GF(2^16) Leopard-RS, SIMD, O(n log n) — the wall-breaker (P2)
@@ -37,6 +37,8 @@ rand = "0.9"
 zeroize = "1"
 
 quinn = { version = "0.11", optional = true }
+rustls = { version = "0.23", optional = true, default-features = false, features = ["ring", "std"] }
+rcgen = { version = "0.13", optional = true, default-features = false, features = ["aws_lc_rs"] }
 tokio = { version = "1", optional = true, features = ["rt-multi-thread", "net", "sync", "macros"] }
 
 [dev-dependencies]