feat(agent-presets): compose each session's agent from a preset cordis.yml

A preset is a directory holding one `agent.cordis.yml`. Mounting it under an
agent's scope context during `setup(agentCtx)` gives that one session its own
tools and prompt sections while every other live session keeps its own.

No registry gains a tier. `dsh-tools` and `dsh-system-prompt` already file
registrations into the calling context's scope layer, and entry contexts chain
to the context a subtree was plugged into, so a composition mounted under
`agent.ctx` is that agent's alone and unwinds with it.

The mount audits itself because a directly-plugged subtree is absent from
`ctx.loader.entries()` and no boot audit covers it. It rejects an unscoped
target, a row that never became usable, and a row that published a service into
the root service realm — that last one is process-global rather than
per-session, and its collision with the next session surfaces as an unhandled
rejection `setup` never observes, leaving a half-composed agent that looks
healthy. The package invariant re-checks that rule on every service
notification, since a row publishing from a timer would escape a one-shot audit.

Raises the `packages/README.md` word ceiling from 920 to 980: the group table
must enumerate every group, and the new `preset/` row is necessary content.

Design: .agents/notes/implemented/architecture/2026-08-03-per-session-agent-presets.md

.agents/notes/implemented/architecture/2026-08-03-per-session-agent-presets.i18n.yaml

@@ -0,0 +1,6 @@
+# Bilingual-pair consistency record (docs/i18n/README.md): the git blob hash of each
+# 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 .agents/notes/implemented/architecture/2026-08-03-per-session-agent-presets.md
+2026-08-03-per-session-agent-presets.md: 408e5a52b15efde162fa1bc6ae1e9ede8a7f0d98
+2026-08-03-per-session-agent-presets.zh.md: a06aea8d7e89c77d374c06908c10a9b0e5029548

.agents/notes/implemented/architecture/2026-08-03-per-session-agent-presets.md

@@ -0,0 +1,46 @@
+# Agent Note: A session's agent is composed from a preset cordis.yml
+
+Status: implemented
+
+English | [中文](2026-08-03-per-session-agent-presets.zh.md)
+
+## Problem
+
+One `dsh` process serves many sessions, but the composition that decides what an agent *is* — its tools, persona, prompt sections, delegation backends — is fixed for the whole process by the `cordis.yml` the launcher booted. A deployment that wants a benchmark-minimal agent beside a full coding agent has to run two processes, and the shipped workaround (`apps/cli/config/core-web.cordis.yml`, a `--config` overlay that disables tool rows) changes every session at once.
+
+The obvious reading of "let a session pick its composition" is that the loader needs a new tier. It does not. [`dsh-tools`](../../../../packages/core/tools/README.md) and [`dsh-system-prompt`](../../../../packages/core/system-prompt/README.md) already file registrations into the calling context's scope layer, and [the agent is a registration scope](2026-07-08-agent-scope-contexts.md). What was missing is a way to point a whole `cordis.yml` at one agent's scope.
+
+## Decision
+
+A **preset** is a directory holding one `agent.cordis.yml`. The agent factory's `setup(agentCtx)` mounts it as a Cordis `include` subtree plugged into that agent's scope context. Entry contexts chain to the context a subtree was plugged into, so every registration inside the preset lands in that agent's layer and unwinds with the agent. No registry gains a tier, and no session already running is touched.
+
+Composition splits into two planes, decided by what must be shared rather than by what feels agent-related:
+
+| Plane | Instances | Contents |
+|---|---|---|
+| Host | one | The registries themselves (`tools`, `systemPrompt`, `agents`, `agent-loop`, `sessions`), cross-session facilities (persistence, query, projections, storage, settings, credentials, telemetry), and the web host |
+| Agent | one per session | What a single agent contributes to those registries: tool plugins, persona and prompt sections, delegation backends, compaction policy |
+
+Model routing stays out of presets. `installAgentLlmTarget` is already the per-agent seam for provider, model, and reasoning effort, and an LLM adapter mounted inside a preset would never be resolved by `agent-loop`, which lives in the host plane.
+
+Mounting is per-session by default. Measured cost for a twelve-row composition is ~3ms and ~600KB per session, so isolation is the cheaper default than any sharing scheme, and a preset authored by a user or by an agent then has the smallest possible blast radius. A preset that genuinely owns an expensive singleton opts into sharing with Cordis's own `isolate` vocabulary: a named realm label is process-global, so two subtrees naming the same label resolve one instance.
+
+## Consequences
+
+**A directly-plugged subtree is invisible to the boot audit.** It never links itself to an `Entry`, so it is absent from `ctx.loader.entries()` and `assertEntriesActivated` cannot see it. The mount audits its own rows instead, reading the tree through an `Include` subclass that publishes it.
+
+**A preset may not publish into the root service realm.** Such a service is process-global rather than per-session, so the second session mounting the same preset collides with the first — and the collision surfaces as an unhandled rejection that `setup` never observes, leaving a half-composed agent that looks healthy. The mount rejects it instead, and the package invariant re-checks on every service notification because a row publishing from a timer or an asynchronous continuation would escape a one-shot audit.
+
+**Failure rolls the agent back.** `setup` runs before publication, so a rejected mount fails `ctx.agents.create()` and leaves nothing behind. This is why `setup` is the one supported call site.
+
+**Fiber membership is object identity, not `uid`.** A `uid` is a per-registry counter, so fibers in two different roots collide on it; comparing by `uid` made one runtime's subtree answer for a service published in another. `ctx.plugin()` returns a thenable `Object.create(fiber)` wrapper that is never identical to the fiber in a parent chain, so the subtree captures its own fiber during construction.
+
+**The preset id is model-visible and must be logged.** It determines the tool set and prompt, so a resumed session has to restore the same composition; recording it is a session fact, not runtime state.
+
+## Alternatives considered
+
+**Add a preset tier to the scoped registries.** `ScopedLayers.merge()` combines the global layer with exactly one exact-scope layer. A middle tier would let many sessions share one mounted composition, but it changes `dsh-scope` and every scope-aware registry to save a cost measured in milliseconds, and it gives a preset's registrations a lifetime no agent owns.
+
+**Make the agent's scope key the preset.** Sessions on one preset would share a layer for free, but per-agent registrations — `installAgentLlmTarget`, per-agent tool restrictions — would then collide across sessions.
+
+**Run each preset as a child process.** [`subagent-dsh-sdk`](../../../../packages/subagent/subagent-dsh-sdk/README.md) already proves a full child harness works, and isolation would be absolute. It also means proxying streaming, approvals, and projections per session, which is a transport project rather than a composition one.

.agents/notes/implemented/architecture/2026-08-03-per-session-agent-presets.zh.md

@@ -0,0 +1,46 @@
+# Agent Note：会话的 agent 由一份 preset cordis.yml 组装而成
+
+Status: implemented
+
+[English](2026-08-03-per-session-agent-presets.md) | 中文
+
+## 问题
+
+一个 `dsh` 进程服务多个会话，但决定 agent（智能体）究竟是什么的那套组装——它的工具、人设、提示词段落、委派后端——由启动器所引导的 `cordis.yml` 一次性固定给整个进程。若某个部署希望一个 benchmark 精简 agent 与一个完整编码 agent 并存，就必须跑两个进程；而现有的变通方案（`apps/cli/config/core-web.cordis.yml`，一个用来禁用工具行的 `--config` 覆盖层）会一次性改变所有会话。
+
+对"让会话自选组装"最直觉的理解，是 loader 需要新增一层。其实不需要。[`dsh-tools`](../../../../packages/core/tools/README.md) 与 [`dsh-system-prompt`](../../../../packages/core/system-prompt/README.md) 本就按调用方上下文的 scope 分层归档注册，而且 [agent 本身就是一个注册 scope](2026-07-08-agent-scope-contexts.md)。此前缺的只是一种把整份 `cordis.yml` 指向某一个 agent scope 的办法。
+
+## 决策
+
+**preset** 是一个目录，其中放置一份 `agent.cordis.yml`。agent 工厂的 `setup(agentCtx)` 把它作为 Cordis `include` 子树，挂载到该 agent 的 scope 上下文之下。entry 上下文沿原型链连到子树被挂载时所在的上下文，因此 preset 内部的每一次注册都落进该 agent 的分层，并随 agent 一起卸载。没有任何注册表新增分层，也没有任何已在运行的会话被触及。
+
+组装划分为两个平面，依据是什么必须共享，而不是什么感觉上与 agent 有关：
+
+| 平面 | 实例数 | 内容 |
+|---|---|---|
+| 宿主 | 一份 | 注册表本身（`tools`、`systemPrompt`、`agents`、`agent-loop`、`sessions`）、跨会话设施（持久化、查询、投影、存储、设置、凭据、遥测），以及 web 宿主 |
+| agent | 每会话一份 | 单个 agent 对这些注册表的贡献：工具插件、人设与提示词段落、委派后端、压缩策略 |
+
+模型路由不进 preset。`installAgentLlmTarget` 已经是 provider、model 与 reasoning effort 的按 agent 可替换点；而挂在 preset 内部的 LLM 适配器永远不会被 `agent-loop` 解析到，因为后者位于宿主平面。
+
+挂载默认按会话进行。实测一份十二行组装每会话约 3ms、约 600KB，因此隔离比任何共享方案都更划算；而由用户或 agent 写出的 preset 也因此拥有尽可能小的影响面。确实自带昂贵单例的 preset，可以用 Cordis 自身的 `isolate` 词汇显式选择共享：命名 realm 的 label 是进程级全局的，因此两棵子树只要写同一个 label 就解析到同一个实例。
+
+## 后果
+
+**直接挂载的子树对启动审计不可见。** 它不会把自己关联到 `Entry`，因此不在 `ctx.loader.entries()` 中，`assertEntriesActivated` 也看不到它。改由挂载过程自行校验各行，通过一个会公开自身 tree 的 `Include` 子类读取。
+
+**preset 不得把服务发布进根 realm。** 这类服务是进程级全局而非按会话的，因此第二个挂载同一 preset 的会话会与第一个相撞——而这次相撞表现为 `setup` 永远观察不到的未处理 rejection，留下一个看起来健康、实则组装到一半的 agent。挂载改为直接拒绝它；本包的运行时不变量还会在每次服务通知时复查，因为从定时器或异步续体中发布的行会绕过一次性审计。
+
+**失败会让 agent 回滚。** `setup` 在发布之前运行，因此挂载被拒绝会让 `ctx.agents.create()` 失败且不留残留。这正是 `setup` 是唯一受支持调用点的原因。
+
+**fiber 归属判定用对象同一性，而非 `uid`。** `uid` 是按 registry 计数的序号，因此两个不同根下的 fiber 会在它上面撞号；按 `uid` 比较曾导致一个运行时的子树为另一个运行时中发布的服务背锅。`ctx.plugin()` 返回的是 thenable 的 `Object.create(fiber)` 包装对象，与父链中出现的 fiber 永远不同一，因此子树在构造时捕获自己的 fiber。
+
+**preset id 对模型可见，必须写入日志。** 它决定工具集与提示词，因此被恢复的会话必须还原同一份组装；记录它属于会话事实，而非运行时状态。
+
+## 考虑过的替代方案
+
+**在 scope 注册表中新增 preset 分层。** `ScopedLayers.merge()` 把全局层与恰好一个精确 scope 层合并。新增中间层可以让多个会话共用一份已挂载的组装，但它要改动 `dsh-scope` 及每个 scope 感知的注册表，换来的只是毫秒级的开销节省，而且会让 preset 的注册获得一个没有任何 agent 拥有的生命周期。
+
+**把 agent 的 scope 键设为 preset。** 同一 preset 上的会话就能免费共享一层，但按 agent 的注册——`installAgentLlmTarget`、按 agent 的工具限制——会跨会话相撞。
+
+**把每个 preset 作为子进程运行。** [`subagent-dsh-sdk`](../../../../packages/subagent/subagent-dsh-sdk/README.md) 已经证明完整的子 harness 可行，隔离性也会是绝对的。但这同时意味着要按会话代理流式输出、审批与投影，那是一个传输层项目，而非组装问题。