Reported expert-cache hit rate excludes --pcie-frac experts, so it rises as tok/s falls #588

The serve log's "decode expert cache hit rate" and the /metrics hit_rate field are the VRAM-resident share of the experts the pool looked up, not the share that avoided the CPU pool. Experts sent over PCIe for the GPU to read (--pcie-frac) are counted in neither cache_hits nor cache_refused, so raising --pcie-frac removes misses from the denominator and raises the reported hit rate even though those experts still have to be fetched and computed on the GPU:

• src/core/expert_source.cpp: in the pool dispatch, if (kind[i] >= 0) { if (kind[i] == 0) ++d.cache_hits; ... continue; } — kind == 1 (PCIe) and kind == 2 (peer) hit neither counter, and only the CPU path below does ++d.cache_refused. d.pcie_experts tracks the offload separately (:1965).
• src/program/generate.cpp computes the rate over hits + admitted + refused and even documents the exclusion: "the VRAM share of the experts the pool looked up while decoding; experts it sent over PCIe for the GPU to read (--pcie-frac) are in neither count".

So the metric is correct as a VRAM-residency figure, but it is presented (and shown in the Monitor tab) as a cache hit rate / health number, and it moves in the opposite direction from end-to-end speed when --pcie-frac changes. Measured on an RTX A3000 12 GB (Swift 1.5 IQ3_XXS, engine 0.1.35, a representative coding conversation):

0.75 reports a 0.78 hit rate while being the slowest arm. This makes the field hard to use as a calibration/health signal and easy to misread (e.g. "hit rate went up, why is it slower?").

Suggestion

Surface the GPU-offloaded share so the resident rate is interpretable — e.g. append the pcie/peer delta to the serve line and expose it in /metrics, or rename the existing field to make the exclusion explicit (vram_hit_rate), or compute the rate over all routed lookups. Happy to implement whichever direction is preferred; I did not want to change the semantics unilaterally since the current behaviour is deliberate. Details/measurements: forks-Strata ops/issues/p8-reduce-misses.md.