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.

packages/bundle/web-app/cordis.patch.yml

@@ -263,14 +263,12 @@
 - id: tool-result-prune
   disabled: true
 
-- id: subagent
-  disabled: true
-
-- id: subagent-spawn
-  disabled: true
-
-- id: subagent-fork
-  disabled: true
+# The subagent registry and its backends STAY in the host plane. `subagents` is
+# a process singleton with a cross-session query surface (`listChildren`,
+# `followup`) that the host api-proxy serves to the browser, and a provider
+# registers under a globally unique name, so a per-session copy would both
+# starve that host row and collide on the second session. What a preset
+# chooses is which delegation TOOLS its agent sees, below.
 
 - id: tool-subagent-control
   disabled: true