Implements WoW-style mount idle behavior when player is stationary:
- Fidget animations: discovered via property search (non-looping, 500-1500ms, stationary, IDs 1-10)
- Triggers random fidget every 6-12 seconds when standing still
- Ambient idle sounds: snorts/breaths for ground mounts, soft wing sounds for flyers
- Triggers random idle sound every 8-15 seconds when stationary
- Both systems reset timers on movement to avoid triggering while riding