docs(llm-pi-ai): state the composition-base assumption for the dict-merge limitation

Maintainer ruling on the review's merge-semantics warning: per-model
reasoning fields belong to the settings document, not cordis.yml entry
config (the shipped composition mounts the adapter dormant), so the
recursive-merge delete gap is a documented posture rather than a tracked
fix; the Known Limitations entry now states the assumption instead of
pointing at the closed #2003.

packages/llm/llm-pi-ai/README.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write packages/llm/llm-pi-ai/README.md
-README.md: c5ebca23ccb4162b65a6e18132970eaf01a50b84
-README.zh.md: f916462bca915bea37c59f7a33a08e1dcc18c4c7
+README.md: eb67ce889193aadbd694d7aae53e47c7d20703be
+README.zh.md: b4b3e3c208702fa10e5f434a70608702d0576fbd

packages/llm/llm-pi-ai/README.md

@@ -186,7 +186,7 @@ Recorded response content appends to the next request and does not invalidate it
 ## Known Limitations and Deferred Work
 
 - **Settings can add or override routes, not remove composition routes** — the user layer merges over the composition `base`, so deleting a `cordis.yml`-provided provider is a composition change; `replace` on the namespace only resets the user layer.
-- **The layered merge has no delete for dict keys** — the settings seam merges the composition `base` and the user layer per key, recursively, so a `reasoningEfforts` level, `modelOverrides` entry, or `compat` field the base declares cannot be removed by the user layer, only overridden — and for `reasoningEfforts` absence *is* the meaning ("not offered"), so a base-declared level stays offered. A `models` list is an array and replaces wholesale, which is the workaround: declare the model there instead. Atomic-leaf merge semantics at the settings seam are tracked in [#2003](https://github.com/deepseek-harness/deepseek-harness/issues/2003).
+- **The layered merge has no delete for dict keys** — the settings seam merges the composition `base` and the user layer per key, recursively, so a `reasoningEfforts` level, `modelOverrides` entry, or `compat` field the base declares cannot be removed by the user layer, only overridden — and for `reasoningEfforts` absence *is* the meaning ("not offered"), so a base-declared level stays offered. This only triggers when a `cordis.yml` entry config declares per-model reasoning fields for the same model the user layer edits; the supported posture is to leave those to the settings document (the shipped composition mounts the adapter dormant), and a `models` list is an array replacing wholesale, which is the in-band escape.
 - **`headers` can carry a credential the redactor never sees** — the profile's `headers` dict is plain strings, so `Authorization` or `api-key` set there is returned verbatim by a redacted `describe()` and rendered by any configuration UI. Store credentials as `apiKeyEnv` references; making the dict write-only is deferred with the rest of the [wire-boundary work](../llm/README.md#known-limitations-and-deferred-work).
 - **A route's catalog never refreshes itself** — the catalog is whatever `settings.yaml` says, so a model list is only as current as its last edit. Nothing here queries a provider for the models it serves; a route gains a model when someone writes one.
 - **One wire protocol per route** — `api` applies to the whole route, so a mixed-protocol catalog route (an OpenAI-style catalog spanning Responses and Chat Completions) cannot host a model of the other protocol, and adding a model such a route does not describe requires naming `api` and moving every model onto it. Splitting the provider across two route keys is the workaround.

packages/llm/llm-pi-ai/README.zh.md

@@ -186,7 +186,7 @@ pi-ai 事件会变为 harness 推理、文本、工具调用、usage 与 finish
 ## 已知限制与暂缓事项
 
 - **settings 能新增或覆盖路由，但不能移除组合路由**：用户层合并在组合 `base` 之上，因此删除 `cordis.yml` 提供的提供方属于组合变更；对该 namespace 执行 `replace` 只会重置用户层。
-- **分层合并对字典键没有删除语义**：settings seam 把组合 `base` 与用户层按键递归合并，因此 base 声明的某个 `reasoningEfforts` 档位、`modelOverrides` 条目或 `compat` 字段，用户层只能覆盖、无法移除——而 `reasoningEfforts` 里缺席本身*就是*语义（「不提供」），于是 base 声明过的档位会一直被提供。`models` 列表是数组、整体替换，这也是规避写法：把该模型改到那里声明。settings seam 的原子叶合并语义在 [#2003](https://github.com/deepseek-harness/deepseek-harness/issues/2003) 跟进。
+- **分层合并对字典键没有删除语义**：settings seam 把组合 `base` 与用户层按键递归合并，因此 base 声明的某个 `reasoningEfforts` 档位、`modelOverrides` 条目或 `compat` 字段，用户层只能覆盖、无法移除——而 `reasoningEfforts` 里缺席本身*就是*语义（「不提供」），于是 base 声明过的档位会一直被提供。只有 `cordis.yml` entry config 为用户层正在编辑的同一模型声明了按模型推理字段才会触发；受支持的姿态是把这些字段留给 settings 文档（shipped 组合以休眠方式挂载该适配器），且 `models` 列表是数组、整体替换，这是体制内的出口。
 - **`headers` 可能承载一条脱敏器看不见的凭据**：profile 的 `headers` 是纯字符串字典，因此设在其中的 `Authorization` 或 `api-key` 会被脱敏后的 `describe()` 原样返回，并被任何配置 UI 渲染出来。请把凭据存为 `apiKeyEnv` 引用；把该字典整体改为只写与其余[协议边界工作](../llm/README.md#known-limitations-and-deferred-work)一并暂缓。
 - **路由的 catalog 不会自我刷新**：catalog 就是 `settings.yaml` 所写的内容，因此模型列表的新鲜度只到最近一次编辑为止。这里没有任何环节会去问提供方它服务哪些模型；路由要多一个模型，得有人写进去。
 - **每条路由只有一种协议格式**：`api` 作用于整条路由，因此混合协议的 catalog 路由（跨 Responses 与 Chat Completions 的 OpenAI 式 catalog）无法承载另一种协议的模型，向这类路由添加它未描述的模型必须点名 `api` 并把全部模型一起迁过去。把该提供方拆成两个路由键是变通办法。