prain: web UI with a model monitor

A clear chat page (markdown, code blocks with copy, stop, new chat, kept in the browser,
drafts shown as such) and a monitor sidebar, a sheet on phones: tokens/s, a live map of the
30 x 128 experts (in VRAM, used now, copied in), VRAM hit rate, copies, context, prompt cache,
GPU VRAM/load/temperature/power/fan. GET /status merges vLLM /metrics, amdgpu sysfs and the
stats file, which now lists the experts in VRAM. /warm answers 202 when a warm-up starts.
README: the int4 kernels, their A/B, 2048-token chunks as a trade, prompt logprobs limit.

examples/gemma4-26b-a4b-rx6600xt.toml

@@ -24,8 +24,8 @@ quant = "int4"                           # then quantized once into an int4 pack
                                          # bf16 | int8 (5.69 MiB/expert) | int4 (3.01 MiB)
 default_tier = "disk"                    # runs on any RAM size; `prain tune` does better
 cache_slots = 15                         # 30 x 15 x 3.01 MiB = 1.32 GiB of VRAM
-stats_path = "../models/packs/gemma4-26b-a4b/stats.json"
-stats_every = 64                         # MoE forward passes between stats/trace writes
+stats_path = "../models/packs/gemma4-26b-a4b/stats.json"  # prain plan and the web monitor read it
+stats_every = 8                          # MoE forward passes between stats/trace writes (~3 ms each)
 trace_path = "../models/packs/gemma4-26b-a4b/trace.jsonl.gz"  # routing trace for sim/tune
 
 [policy]              # which expert a cache slot gives up