Created specific idle sound pool using only horse snorts and whinnies.
Re-enabled idle sounds with much longer interval (20-40 seconds).
Changes:
- Added horseIdleSounds_ pool: mHorseStand3A (snort) + mHorseAggroA (whinny)
- Updated playIdleSound() to use dedicated pool instead of mixed breath sounds
- Increased idle sound interval from 8-15s to 20-40s (less frequent)
- Removed flying mount idle sounds (too aggressive)
- Increased volume slightly (0.35x) for better audibility
