llama.cpp Q8 mmproj matches FP16

Anecdotal, but directionally useful: for local multimodal inference, `mmproj` precision may matter far less than the conventional FP16 default suggests.

• –Across most models, Q8 and FP16 changed phrasing and confidence more than actual image understanding
• –Qwen3.5 0.8B seemed to gain a bit from FP16, which may be more about tiny text-model instability than vision precision
• –Qwen3.5 4B was the surprise: FP16 sometimes overfocused on irrelevant detail, while Q8 picked up the obvious object
• –The post’s setup is CPU-only, temp 0, and self-described as informal, so this is not a benchmark verdict
• –Still, it points to a practical default for local runs: Q8 mmproj may be enough unless you have a specific reason to keep FP16