fix(agent-presets,connection): reclaim a deleted default, unpin a fence beside an open gate

Deleting the preset a user default names left the setting pointed at an id
nothing will ever supply again, and every session created without an explicit
pick then failed to start — the delete dialog called it 'new sessions cannot
select it', which understates a hard creation error. `remove` now clears the
user layer when it named the preset just deleted, exposing the deployment's own
default underneath. Storing a default that does not exist YET stays deliberate:
the roster is a live directory, so a name absent now may exist by the time a
session asks, and `resolve` still reports that case.

`agentPreset.select` also leaves the loopback set. It was pinned as a real
escalation — one preset mounts the toolset that edits the live runtime — but
`session.create` already takes an `agentPreset`, so pinning only the switch left
the same capability one method over. The deeper reason is that the capability is
not the preset's to grant: the deployment's own default already carries `bash`
and the filesystem tools, so any caller that may start a session at all can
already run commands as this process. `read`/`write`/`remove` stay pinned on
their own footing — those touch files, not sessions.

.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: 4909f6433f0a528c9e16f842afec11be382b1d44
-2026-08-03-per-session-agent-presets.zh.md: f6a751bf75806f59f168fd9beec0d4b4dc187f3a
+2026-08-03-per-session-agent-presets.md: 6f1643c25008c3363cb10adb7fbff7afeea31cbe
+2026-08-03-per-session-agent-presets.zh.md: 7afe9ade5c98fadb96384a7e0acd47531c370e0c

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

@@ -53,7 +53,7 @@ Which preset an unnamed session gets is a user setting (`agent-presets.default`)
 
 **Switching is allowed only while a session is blank.** Once a turn has run, that history was produced under the preset's tools and swapping them would strand logged tool calls, so `agentPreset.select` answers `agent-preset-locked`. A blank switch keeps the agent and the session and replaces only the subtree, because the host discards the `AgentHandle` it creates and there is no delete RPC — and keeping them is the better outcome anyway, since the session id, its workspace attachment, and its projections all stay put. The swap is unmount-then-mount (two compositions would register the same tool names into one layer), so it resolves the new preset before tearing anything down and restores the previous one when the new mount fails.
 
-**Authoring a preset is an RPC, and a privileged one.** A composition is a file, but "edit it on the filesystem" is not a browser affordance, so the roster gained `read`/`write`/`remove` beside `select`. All four are loopback-pinned: a composition names the plugins a session runs, so reading one is reconnaissance, writing one is arbitrary capability, and selecting one can move a session onto a preset that edits the live runtime. `list` deliberately stays ordinary — ids and trust only, and a LAN client's picker needs it. Containment is a property of the id (`[a-z0-9][a-z0-9-]*`), checked before it becomes a directory name rather than by inspecting the joined path afterwards; the text is parsed with the loader's own schema and dialect, so a save cannot leave a file no session could load. Shipped presets are refused for writes and deletes, because the deployment's copy is what a broken local preset is compared against — which also makes "duplicate, then edit" the authoring path rather than an afterthought.
+**Authoring a preset is an RPC, and a privileged one.** A composition is a file, but "edit it on the filesystem" is not a browser affordance, so the roster gained `read`/`write`/`remove` beside `select`. Those three are loopback-pinned: a composition names the plugins a session runs, so reading one is reconnaissance and writing one is arbitrary capability. `list` and `select` deliberately stay ordinary. The roster carries ids and trust only, and a LAN client's picker needs it; and choosing a preset looked like escalation — one of them mounts the toolset that edits the live runtime — but `session.create` already takes an `agentPreset`, so pinning only the switch would have left the same capability one method over. The capability is not the preset's to grant either: the deployment's own default already carries `bash` and the filesystem tools, so any caller that may start a session at all can already run commands as this process. Containment is a property of the id (`[a-z0-9][a-z0-9-]*`), checked before it becomes a directory name rather than by inspecting the joined path afterwards; the text is parsed with the loader's own schema and dialect, so a save cannot leave a file no session could load. Shipped presets are refused for writes and deletes, because the deployment's copy is what a broken local preset is compared against — which also makes "duplicate, then edit" the authoring path rather than an afterthought.
 
 **A service with a consumer outside the agent plane cannot move into a preset.** The aggressive split moved the `subagents` registry and its spawn/fork backends into the delegation group's entry-local realm, and `dsh web` then failed to boot: `dsh-host-apiproxy` is a HOST row that injects `subagents` to answer the browser's cross-session queries (`listChildren`, `followup`), so it waited forever for a service only sessions now provided. A per-session copy is wrong twice over — a provider name registers once, so the second session would have collided anyway. The registry and its backends are host-plane; the preset contributes the delegation TOOLS, which resolve the host registry. `workflows` stays entry-local because nothing outside an agent reads it. Grepping injectors is what should have caught this and did not: the search has to include the host packages, not just the agent-plane ones.
 

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

@@ -54,7 +54,7 @@ Status: implemented
 
 **只有空白会话才允许切换。** 一旦跑过任何轮次，那段历史就是在该 preset 的工具下产生的，替换会留下无法执行的已记录 tool call，因此 `agentPreset.select` 返回 `agent-preset-locked`。空白期的切换保留 agent 与 session，只替换子树——因为宿主丢弃了它创建的 `AgentHandle`，也没有 delete RPC；而保留它们本身就是更好的结果，会话 id、workspace 挂接与 projections 都原地不动。该替换是"先卸后装"（两份组装会把同名工具注册进同一分层），因此它在拆除任何东西之前先解析新 preset，并在新组装装载失败时恢复原来的那一份。
 
-**创作 preset 是一次 RPC，而且是特权 RPC。** 组装是一个文件，但“去文件系统里改它”并不是浏览器能提供的操作，因此名单在 `select` 之外新增了 `read`/`write`/`remove`。这四者都被固定在环回地址：组装指明了一个会话所运行的插件，因此读取它是侦察，写入它是任意能力，而选择它可以把会话切到一个能编辑活动运行时的 preset 上。`list` 刻意保持为普通方法——只有 id 与信任级别，而局域网客户端的选择器需要它。约束是 id 自身的性质（`[a-z0-9][a-z0-9-]*`），在它成为目录名之前就检查，而不是事后再去审视拼接出的路径；文本使用 loader 自身的 schema 与方言解析，因此保存不会留下任何会话都无法加载的文件。随部署提供的 preset 拒绝写入与删除，因为部署自带的那一份正是用来对照有问题的本地 preset 的——这也让“先复制、再编辑”成为创作路径本身，而非事后补充。
+**创作 preset 是一次 RPC，而且是特权 RPC。** 组装是一个文件，但“去文件系统里改它”并不是浏览器能提供的操作，因此名单在 `select` 之外新增了 `read`/`write`/`remove`。这三者被固定在环回地址：组装指明了一个会话所运行的插件，因此读取它是侦察，写入它是任意能力。`list` 与 `select` 刻意保持为普通方法。名单只携带 id 与信任级别，而局域网客户端的选择器需要它；至于选择本身，它看起来像提权——其中一个 preset 会挂载可编辑活动运行时的工具集——但 `session.create` 本就接受 `agentPreset`，只固定切换会把同一能力留在隔壁一个方法上。这份能力也不由 preset 授予：部署自带的默认 preset 本就带着 `bash` 与文件系统工具，因此任何被允许开启会话的调用方，早已能以本进程的身份执行命令。约束是 id 自身的性质（`[a-z0-9][a-z0-9-]*`），在它成为目录名之前就检查，而不是事后再去审视拼接出的路径；文本使用 loader 自身的 schema 与方言解析，因此保存不会留下任何会话都无法加载的文件。随部署提供的 preset 拒绝写入与删除，因为部署自带的那一份正是用来对照有问题的本地 preset 的——这也让“先复制、再编辑”成为创作路径本身，而非事后补充。
 
 **在 agent 平面之外还有消费方的服务，不能搬进 preset。** 激进拆分把 `subagents` 注册表连同 spawn/fork 后端一起搬进了 delegation 组的 entry-local realm，于是 `dsh web` 直接起不来：`dsh-host-apiproxy` 是宿主行，它注入 `subagents` 来回答浏览器的跨会话查询（`listChildren`、`followup`），因而永远等待一个此刻只有会话才提供的服务。按会话各一份在两个层面上都是错的——provider 名只能注册一次，第二个会话本来也会相撞。注册表与后端属于宿主平面；preset 贡献的是委派**工具**，它们解析宿主注册表。`workflows` 保持 entry-local，因为 agent 之外没有任何东西读它。本该拦下它的是「检索注入方」这一步，而它没拦住：检索必须覆盖宿主包，而不只是 agent 平面的包。