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/movement.rs

@@ -434,15 +434,15 @@ pub fn validate_movement(
                 Some(MovementStance::Careful) => 0.3,
                 Some(MovementStance::Crouch) => 0.15,
             };
-            commands.entity(entity).insert(SoundEventEmitter::new(
-                SoundEvent::at(
+            commands
+                .entity(entity)
+                .insert(SoundEventEmitter::new(SoundEvent::at(
                     &target,
                     SoundEventKind::Footstep,
                     intensity,
                     SoundRange::Close,
                     None,
-                ),
-            ));
+                )));
         }
         commands.entity(entity).remove::<MoveIntent>();
     }