feat(fv-ml1): rebalance GPUs 0/1 by usage; contexts to published maximums; gen-small default output cap

Layout: GPU 0 = cyberprev (KV 16 -> 15 GiB, 1.29x), erp-seat (moved from
GPU 1, KV 8.49 -> 5.5 GiB, 1.32x), voices (ctx 8,192 -> 40,960, its native
maximum, KV 6 GiB, 1.07x), coder (moved from GPU 1, ctx 16,384 -> 32,768,
the card maximum, 2.35x), parakeet-nemo. GPU 1 = gen-small (moved from
GPU 0, 5.5 GiB, 1.76x), meromero-rp (22 GiB, 1.32x), intern-decision.

Sizing rule: KV >= 1.25x max context rounded up to 0.5 GiB, checked against
7 days of LiteLLM traffic and the engines' own KV-usage logs. Each card keeps
spare memory for its bursty tenant (parakeet's cap on GPU 0, intern-decision's
32k call on GPU 1). YaRN extensions are not enabled: they do not fit, and the
Qwen cards warn static YaRN degrades short prompts.

gen-small gets --override-generation-config max_new_tokens 32768. It applies
only to requests that omit max_tokens (vLLM get_max_tokens) and answers 9
runaway ~260k-token replies in 7 days; the longest normal reply was 6,357.

Applied with playbooks/fv-ml1-rebalance-20261005.yaml (boot-check guard and
health/KV verification per seat); all nine seats healthy, gateway smoke
tests pass.

stacks/gen-small-seat/compose.yaml

@@ -1,5 +1,5 @@
 # gen-small-seat — a fast, cheap "gen-small" seat: Qwen3.6-35B-A3B (3B active MoE),
-# Heretic-abliterated, on fv-ml1 GPU 0, :8026.
+# Heretic-abliterated, on fv-ml1 GPU 1, :8026.
 #
 # WHY: a tiny-active (A3B = ~3B active of 35B total) gen tier for high-volume / low-latency
 # work, complementing the big gen seat (flash-next :8022). Operator-directed 2026-09-14.
@@ -59,6 +59,13 @@ services:
       # attention footprint make this cheap; tuned to a sane concurrency band, not max.
       - --kv-cache-memory
       - "${GEN_SMALL_KV_CACHE_MEMORY:-5905580032}"
+      # Default output cap (2026-10-05, Prime). A request that OMITS max_tokens stops at 32,768
+      # instead of max_model_len - prompt; an explicit max_tokens still wins (vLLM get_max_tokens:
+      # request value first, generation-config max_new_tokens only as the fallback). Reason: 9
+      # runaway replies in 7 days, each ~260k tokens over 20+ min (albok-nemi, all-agents-local),
+      # while the longest normal reply was 6,357 tokens.
+      - --override-generation-config
+      - '{"max_new_tokens": 32768}'
       - --max-model-len
       - "${GEN_SMALL_MAX_MODEL_LEN:-262144}"
       - --max-num-seqs