feat(server): initialize Rust/bevy_ecs simulation server

Server boilerplate epic (276) complete. Establishes the Rust simulation
server foundation per D-020 (subprocess/IPC architecture).

Structure:
- bevy_ecs 0.18 + bevy_app 0.18, MessagePack serialization (rmp-serde)
- SimulationPlugin with deterministic resources: SimulationTime (D-031),
  SimRng (D-030), InputQueue (D-010)
- Core IPC types: ObserverSnapshot, PlayerInput, SimBridge trait (D-020)
- CauseChain production component for provenance tracking (D-030)
- SimulationTier types with LRU eviction support (D-026)
- NPC 10-axis model components (D-024)
- 15 tests: inline unit tests + integration smoke/serialization tests
- make ci-server passes (clippy, fmt, build, test)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/simulation/mod.rs

@@ -0,0 +1,25 @@
+// Simulation module - Core simulation plugin and systems
+// Implements deterministic tick-based simulation (D-010 principle 4)
+
+use bevy_app::prelude::*;
+
+pub mod input;
+pub mod rng;
+pub mod tier;
+pub mod time;
+
+/// Core simulation plugin
+/// Manages simulation time, RNG, input processing, and tier transitions
+pub struct SimulationPlugin;
+
+impl Plugin for SimulationPlugin {
+    fn build(&self, app: &mut App) {
+        // Initialize core simulation resources
+        app.init_resource::<time::SimulationTime>()
+            .insert_resource(rng::SimRng::new(0))
+            .init_resource::<input::InputQueue>()
+            .add_systems(Update, time::advance_tick);
+
+        tracing::debug!("SimulationPlugin initialized");
+    }
+}