frank-default-small: prefill-max ncmoe 35 / ubatch 3072

Prefill is the priority for this workload. Switch from decode-max
(ncmoe 32 / ubatch 1024) to prefill-max:
- n-cpu-moe 35, ubatch 3072: prefill ~1458 t/s (top tier), gen ~45.4 t/s,
  ~1.2 GiB headroom at the 800k pool.
- Gen is independent of ubatch; ub 3072 reaches best prefill with no
  decode cost. Docs synced (benchmark Chosen State, deployment, specs).

docs/frank-default-small-benchmark.md

@@ -101,19 +101,24 @@ and fails, which matches the recorded OOMs at `ncmoe 32` and `33`.
 
 ## Chosen State
 
-The chosen state balances generation speed against prefill speed and OOM
-headroom:
+Prefill speed is the priority for this workload, so the final state takes
+the top prefill tier while keeping a safe headroom margin:
 
 ```
---n-cpu-moe 32     # 8 expert layers on GPU
+--n-cpu-moe 35     # 5 expert layers on GPU
 --batch-size   8192
---ubatch-size  1024
+--ubatch-size  3072
 ```
 
-This gives generation about 48.7 t/s (7 percent above the previous
-`ncmoe 35`) while keeping the box above the OOM boundary. If prefill speed
-matters more than generation, use `ncmoe 34 - ubatch 2048`. If stability
-headroom matters most, use `ncmoe 34 - ubatch 1536`.
+This gives prefill about 1458 t/s at 16384 prompt tokens, generation about
+45.4 t/s, and about 1.2 GiB of headroom at the 800000-token pool. Both are
+chosen because generation does not depend on `ubatch`: `ubatch 3072` reaches
+the best prefill speed with no cost to decode.
+
+If decode speed matters more than prefill, swap to `ncmoe 32 - ubatch 1024`
+(generation about 48.7 t/s, prefill about 766 t/s, about 1.0 GiB headroom).
+If stability headroom matters most, use `ncmoe 34 - ubatch 1536` (about 2.0
+GiB headroom).
 
 ## Limitations