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/input.rs

@@ -0,0 +1,77 @@
+// Input processing system
+// Timestamped player input events for deterministic simulation (D-010 principle 4)
+// PlayerInput: semantic actions (MoveNorth, Interact, UsePerceptionMode)
+
+use crate::bridge::types::PlayerInput;
+use bevy_ecs::prelude::*;
+use std::collections::VecDeque;
+
+/// Queue of pending player inputs, ordered by tick
+#[derive(Resource, Debug, Default)]
+pub struct InputQueue {
+    queue: VecDeque<PlayerInput>,
+}
+
+impl InputQueue {
+    /// Add a new input to the queue
+    pub fn push(&mut self, input: PlayerInput) {
+        self.queue.push_back(input);
+    }
+
+    /// Drain all inputs for ticks <= the given tick
+    /// Returns inputs in FIFO order
+    pub fn drain_for_tick(&mut self, tick: u64) -> Vec<PlayerInput> {
+        let mut result = Vec::new();
+        while let Some(front) = self.queue.front() {
+            if front.tick <= tick {
+                result.push(self.queue.pop_front().unwrap());
+            } else {
+                break;
+            }
+        }
+        result
+    }
+
+    /// Get the current queue length
+    pub fn len(&self) -> usize {
+        self.queue.len()
+    }
+
+    /// Check if the queue is empty
+    pub fn is_empty(&self) -> bool {
+        self.queue.is_empty()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::bridge::types::PlayerAction;
+
+    #[test]
+    fn drain_returns_inputs_up_to_tick() {
+        let mut queue = InputQueue::default();
+        queue.push(PlayerInput {
+            tick: 1,
+            action: PlayerAction::MoveNorth,
+        });
+        queue.push(PlayerInput {
+            tick: 2,
+            action: PlayerAction::MoveSouth,
+        });
+        queue.push(PlayerInput {
+            tick: 5,
+            action: PlayerAction::Interact,
+        });
+        let inputs = queue.drain_for_tick(3);
+        assert_eq!(inputs.len(), 2);
+        assert_eq!(queue.len(), 1);
+    }
+
+    #[test]
+    fn drain_empty_queue_returns_empty() {
+        let mut queue = InputQueue::default();
+        let inputs = queue.drain_for_tick(10);
+        assert!(inputs.is_empty());
+    }
+}