SleepWalk: A Three-Tier Benchmark for Stress-Testing Instruction-Guided Vision-Language Navigation. - Niyati Rawal; Sushant Ravva; Shah Alam Abir; Saksham Jain; Aman Chadha; Vinija Jain; Suranjana Trivedy; Amitava Das 001 (CoRR, 2026)