§3.3 reframe: hot pin failure is uniformly-slow workers, not max/median ratio

User pointed out the apparent paradox: in fig_b3_per_worker_ttft_p90, unified
has hotspot index 3.67 while sticky has 2.73, yet unified e2e p90 is roughly
half of sticky's. Resolution: hotspot index (max/median) is a *ratio* and
misleading on its own. Per-worker absolute TTFT p90:

  sticky : median 20.3s, max 55.4s -> system e2e p90 34.6s
  unified: median 10.3s, max 37.7s -> system e2e p90 18.0s

Mechanism: top 1% sessions own 46.5% input mass and there are more hot
sessions than instances (8), so sticky's hash binding gives *every* worker
its own hot session and the median worker is also slow. Unified's LMetric
fallback re-routes cold/new sessions away from hot affinity instances,
preserving 7/8 worker speed. System p90 is dominated by the majority of
requests landing on fast workers, hence the 2x e2e gap.

Changes:
- Replace §3.3 figure with figs/f4c_per_worker_ttft.png (per-worker bars)
  instead of figs/f4c_apc_vs_hotspot_tradeoff.png (the ratio scatter)
- §3.3 narrative in PAPER_OUTLINE.md and MEETING.md rewritten around
  absolute median + max + system e2e p90 instead of hotspot ratio
- Add a §3.3 sub-finding: "hot pin failure must be measured with
  per-worker absolute latency, not normalized ratio"
- Keep the scatter as supplementary for §5 multi-policy summary

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

MEETING.md

@@ -47,11 +47,18 @@ LMetric 56.9%、load_only 54.1%、capped 31.6% APC，远低于 79.6% 上界。23
 
 agentic 平均请求 33.6k token 需 3.3GB KV；4P+4D / 6P+2D 在 agentic regime 都穿过 90% 内存墙。**TTFT p50 暴涨 62-72x，成功率 99.5% → 52-68%**。
 
-### Pure sticky / current unified：hot pin
+### Pure sticky：全员被 hot session 拖累
 
-![](figs/f4c_apc_vs_hotspot_tradeoff.png)
+![](figs/f4c_per_worker_ttft.png)
 
-APC 拉到 77-79%（接近上界），但 hotspot index 翻倍：sticky 2.73、unified 3.66 vs lmetric 2.25、load_only 1.29。skew 中的大 session 被锁在单 instance 上，造成 prefill-decode 干扰。
+注意 hotspot index（max/median 比值）单独看会误导：sticky 的 hotspot=2.73 比 unified 的 3.67 *低*，但**绝对值**告诉我们 sticky 是"全员一起慢"，unified 是"一个 worker 牺牲、其他 7 个快"：
+
+| | median worker TTFT p90 | max worker | system e2e p90 |
+|---|---:|---:|---:|
+| sticky | **20.3s** | 55.4s | **34.6s** |
+| unified | **10.3s** | 37.7s | **18.0s** |
+
+机制：top 1% 的 session 占 46.5% input 量、且 hot session 数量多于 instance 数（8 个），sticky 的 hash 绑定让 **每个 worker 都自己承接一份 hot session**，median worker 也被拖慢。Unified 用 LMetric fallback 把 cold/new session 重路由到非 hot worker，保留 7/8 worker 的速度。系统 p90 由大多数请求决定，所以 unified 几乎 2x 快。
 
 ---