fix(simulation): Clippy cleanup and CI enforcement (#635)

Fix all Clippy warnings across the server codebase (2411 insertions, 1341
deletions). Raise type-complexity-threshold to 750 and too-many-arguments
to 12 in .clippy.toml for idiomatic Bevy ECS system signatures. The server
now passes `cargo clippy -- --deny warnings` cleanly.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/src/simulation/spatial.rs

@@ -173,7 +173,10 @@ mod tests {
         index.update(e_near, TilePosition::new(5, 6, 0));
 
         let in_range = index.entities_in_range(&center, 2);
-        assert!(!in_range.contains(&e_at), "entity at center should be excluded");
+        assert!(
+            !in_range.contains(&e_at),
+            "entity at center should be excluded"
+        );
         assert!(in_range.contains(&e_near));
     }
 
@@ -331,7 +334,10 @@ mod tests {
         let in_range = index.entities_in_range(&center, 1);
         assert!(in_range.contains(&e_dist1_x));
         assert!(in_range.contains(&e_dist1_y));
-        assert!(!in_range.contains(&e_dist2), "distance 2 must not appear in radius-1 result");
+        assert!(
+            !in_range.contains(&e_dist2),
+            "distance 2 must not appear in radius-1 result"
+        );
     }
 
     /// Diagonal: Manhattan distance covers all 4 orthogonal directions.
@@ -348,9 +354,9 @@ mod tests {
 
         let center = TilePosition::new(10, 10, 0);
         index.update(north, TilePosition::new(10, 11, 0)); // distance 1
-        index.update(south, TilePosition::new(10, 9, 0));  // distance 1
-        index.update(east, TilePosition::new(11, 10, 0));  // distance 1
-        index.update(west, TilePosition::new(9, 10, 0));   // distance 1
+        index.update(south, TilePosition::new(10, 9, 0)); // distance 1
+        index.update(east, TilePosition::new(11, 10, 0)); // distance 1
+        index.update(west, TilePosition::new(9, 10, 0)); // distance 1
         index.update(corner, TilePosition::new(11, 11, 0)); // distance 2
 
         let in_range = index.entities_in_range(&center, 2);
@@ -425,7 +431,11 @@ mod tests {
         }
 
         let in_range = index.entities_in_range(&center, 200);
-        assert_eq!(in_range.len(), 10, "radius 200 should include all 10 entities");
+        assert_eq!(
+            in_range.len(),
+            10,
+            "radius 200 should include all 10 entities"
+        );
     }
 
     /// Remove one entity from a multi-entity index, others remain.
@@ -500,7 +510,11 @@ mod tests {
 
         {
             let idx = world.resource::<NaiveSpatialIndex>();
-            assert_eq!(idx.entities_at(&start).len(), 1, "entity should be at start after first sync");
+            assert_eq!(
+                idx.entities_at(&start).len(),
+                1,
+                "entity should be at start after first sync"
+            );
         }
 
         // Update position
@@ -511,8 +525,15 @@ mod tests {
 
         {
             let idx = world.resource::<NaiveSpatialIndex>();
-            assert!(idx.entities_at(&start).is_empty(), "old position should be cleared");
-            assert_eq!(idx.entities_at(&dest).len(), 1, "entity should be at new position");
+            assert!(
+                idx.entities_at(&start).is_empty(),
+                "old position should be cleared"
+            );
+            assert_eq!(
+                idx.entities_at(&dest).len(),
+                1,
+                "entity should be at new position"
+            );
         }
     }
 }