The test asserted strictly descending bits_per_channel across ALL levels,
but q4_0 (4.0 bits) is a standard fallback that comes after turbo2 (1.5 bits)
despite having more bits. These are different quantization schemes:
TurboQuant vs standard GGUF.
Fix: separate the assertion into two checks:
1. TurboQuant levels (turbo4 > turbo3 > turbo2) must have strictly
descending bits_per_channel
2. Standard fallback(s) must come after all TurboQuant levels in the list
