feat(app-boot): register cordis:group beside cordis:include

A composition that shares one `isolate` realm across rows needs a
`cordis:group` row, and a preset living outside this workspace — the
authored ones under the Harness home — cannot resolve
`@cordisjs/plugin-group` by name: Node's upward `node_modules` walk
never reaches the harness from there. Registering it as a loader builtin
beside `cordis:include` loads both through the ambient module pipeline
instead.

Record it in the preset Agent Note, which leans on the realm vocabulary
without saying where the group row comes from, and drop the preset
README's limitation claiming this builtin is unavailable — it described
the state this change ends.

The test's assertion had a vacuous escape: `provide` mints the root
symbol unconditionally, so the `rootKey === undefined` disjunct could
never hold and the comment claiming the root realm never learned the
name was wrong. Pin both halves — the symbol exists, nothing is stored
under it — and clean up the global the fixture writes.

.agents/notes/implemented/architecture/2026-08-03-per-session-agent-presets.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 .agents/notes/implemented/architecture/2026-08-03-per-session-agent-presets.md
-2026-08-03-per-session-agent-presets.md: ee6303e5f52234d7eaf6768043c92a15e4e5399f
-2026-08-03-per-session-agent-presets.zh.md: 5a2e1c3d8d0564f06c75785e1080b53740751355
+2026-08-03-per-session-agent-presets.md: dbe4188fe16a01b51f01cddf8a2387471e5e00a9
+2026-08-03-per-session-agent-presets.zh.md: aa7792a7db3a686b74f19ace130ad8f7b6d2feb6

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

@@ -29,6 +29,8 @@ Mounting is per-session by default. Measured cost for a twelve-row composition i
 
 **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 can only name a group because the app registers one.** Sharing a realm across rows is a `cordis:group` row, and a preset living outside this workspace — the authored ones under the Harness home, which is the point — cannot resolve `@cordisjs/plugin-group` by name: Node's upward `node_modules` walk never reaches the harness from there. `boot()` therefore registers `cordis:group` beside `cordis:include` as a loader builtin, so both load through the ambient module pipeline rather than through the included tree's own specifier resolution. Without it the `isolate` vocabulary above is expressible one row at a time only, and a provider could never be grouped with its consumers.
+
 **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.

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

@@ -29,6 +29,8 @@ Status: implemented
 
 **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 能写出 group，是因为 app 注册了它。** 跨行共享 realm 就是一个 `cordis:group` 行，而住在本工作区之外的 preset——也就是 Harness home 下由人或 agent 创作的那些，正是这套设计的目的——无法按名字解析 `@cordisjs/plugin-group`：Node 向上查找 `node_modules` 的路径从那里永远走不到 harness。因此 `boot()` 把 `cordis:group` 与 `cordis:include` 并排注册为 loader builtin，两者都经由环境模块管线加载，而不依赖被包含树自身的说明符解析。没有它，上文那套 `isolate` 词汇就只能一行一行地表达，提供方也永远无法与它的消费方归入同一组。
+
 **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。