fix(web): keep the subagent registry in the host plane

`dsh web` failed to boot: the aggressive plane split moved `subagents` and
its spawn/fork backends into the preset's entry-local realm, but
`dsh-host-apiproxy` is a host row that injects `subagents` to answer the
browser's cross-session queries, 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 go back to the host composition; the presets
keep the delegation TOOLS, which resolve that host registry. `workflows`
stays entry-local: nothing outside an agent reads it.

The web real-composition test could not have caught this, because it
disabled `api-gateway` — the very row whose pending injection names the
break. It now boots with the api-proxy enabled and the browse directory
picker substituted, so the boot audit covers the whole host-plane injection
graph. Re-introducing the old split makes it fail with the three pending
entries, which is how this was verified.

apps/cli/config/agent-presets/standard/agent.cordis.yml

@@ -172,29 +172,21 @@
 
 # ── delegation and workflows ────────────────────────────────────────────────
 
-# Every backend and every tool that reaches `subagents` or `workflows` shares
-# one realm: a consumer left outside it would resolve the host's registry
-# instead, which this preset does not populate.
+# The `subagents` registry and its spawn/fork backends live in the HOST
+# composition: the registry is a process singleton whose cross-session queries
+# the api-proxy serves to the browser, and a provider name may only be
+# registered once. This preset contributes the delegation TOOLS, which resolve
+# that host registry.
+#
+# `workflows` is different — nothing outside an agent reads it — so every row
+# that reaches it shares one entry-local realm here, and a consumer left
+# outside would resolve a host registry this preset does not populate.
 - id: delegation
   name: cordis:group
   group: true
   isolate:
-    subagents: true
     workflows: true
   config:
-    - id: subagent
-      name: '@deepseek-ai/dsh-subagent'
-
-    - id: subagent-spawn
-      name: '@deepseek-ai/dsh-subagent-spawn'
-      config:
-        providerName: spawn
-
-    - id: subagent-fork
-      name: '@deepseek-ai/dsh-subagent-fork'
-      config:
-        providerName: fork
-
     - id: tool-subagent-control
       name: '@deepseek-ai/dsh-tool-subagent-control'