fix(server): address PR #14 review — ordering, docs, version pin

- Fix NpcPlugin system ordering: .before(compute_paths) instead of
  .after(advance_tick) so PathRequests are picked up same frame
- Fix stale doc comment in interpretation.rs: system runs BEFORE
  knowledge events, not after
- Add TODO(v0.2) on RelationshipGraph about information boundary
  limitation for multiplayer
- Document cardinal-only movement as deliberate v0.1 choice
- Add comment on manhattan_distance u32::MAX fallback for cross-z
- Pin pathfinding crate to 4.11

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

server/src/simulation/pathfinding.rs

@@ -55,6 +55,8 @@ pub struct PathBlocked;
 
 /// System: compute paths for entities with PathRequest components.
 /// Uses A* over the WalkabilityMap with cardinal movement (4 neighbors).
+/// Cardinal-only is a deliberate v0.1 simplification: diagonal movement
+/// would require √2 cost handling and diagonal wall-clipping checks.
 /// Removes PathRequest and inserts ComputedPath or PathBlocked.
 pub fn compute_paths(
     mut commands: Commands,
@@ -90,6 +92,8 @@ pub fn compute_paths(
                     .filter(|neighbor| walkability.can_move_to(neighbor))
                     .map(|neighbor| (neighbor, 1u32))
             },
+            // manhattan_distance returns None for cross-z-level pairs;
+            // u32::MAX makes A* deprioritize those nodes (v0.1: single z-level)
             |pos| pos.manhattan_distance(&goal).unwrap_or(u32::MAX),
             |pos| *pos == goal,
         );