feat(simulation): add ListeningFocus eavesdrop positioning (#426)

New ListeningFocus component tracks stationary_ticks for eavesdrop
mechanic. Increments when position unchanged, resets on movement.
Sprint stance blocks accumulation, Careful reduces threshold from
30 to 20 ticks. Registered in SimulationPlugin after validate_movement.

17 tests covering all stances, thresholds, and edge cases.

Ref: D-053 (stance system), D-018 (sound model)

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

server/src/simulation/mod.rs

@@ -7,6 +7,7 @@ use bevy_ecs::schedule::IntoScheduleConfigs;
 pub mod input;
 pub mod interaction;
 pub mod inventory;
+pub mod listening;
 pub mod monologue;
 pub mod movement;
 pub mod path_follow;
@@ -35,8 +36,8 @@ impl Plugin for SimulationPlugin {
                     path_follow::follow_paths.after(pathfinding::compute_paths),
                     movement::validate_movement.after(path_follow::follow_paths),
                     path_follow::cleanup_path_blocked.after(movement::validate_movement),
-                    time::advance_tick
-                        .after(path_follow::cleanup_path_blocked),
+                    listening::update_listening_focus.after(movement::validate_movement),
+                    time::advance_tick.after(path_follow::cleanup_path_blocked),
                 ),
             );