Implements the StartupMessage protocol: client generates world_seed in
SessionManager.new_game(), sends it after handshake, server uses it to
seed SimRng and sample EntanglementConfig.
EntanglementConfig samples flat ∈ [25,35]%, intrigue ∈ [15,25]%, mundane
as remainder (D-029). Same seed produces identical config (D-010
determinism). Different seeds produce distinct configs in ≥90% of pairs.
Protocol flow: HandshakeMessage (server→client) → StartupMessage with
world_seed (client→server) → SimRng initialization → tick loop.
10 Rust tests (determinism, variation, bounds, sum invariant).
9 GDScript test stubs + 2 encode tests for client-side pipeline.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
jpmschweitzerandClaude Opus 4.6
d591f44b35