refactor(gui): one plugin-package shape — dshClient manifests, clientBundle preset, purity gate over all nine

Every client plugin package carries dshClient ({platform, inject,
immediately?}) and emits lib/client.js through the shared clientBundle
preset; exports["./client"] points at the bundle. The infrastructure
tier (connection, runtime, ui-theme, i18n, hmr) declares immediately: true
in its manifest — absent means lazy. The bundle purity gate covers all
nine packages: platform modules stay external, INLINE_SAFE wire layers
inline, any other cross-plugin value import is a build error. Migrations
that rule forced: scopeOf became a SessionsService method and
transportError moved into dsh-host-apiproxy's wire layer; the store
engine stays in runtime under a documented temporary exemption
(TODO(webload/store-rehome)).

packages/host/apiproxy/src/api/index.ts

@@ -39,7 +39,7 @@ export type {
 } from './rpc.ts'
 
 // ---- Errors and ids ----
-export { RpcId } from './rpc.ts'
+export { RpcId, transportError } from './rpc.ts'
 export type { RpcError, RpcErrorCode, RpcErrorDetailsMap, RpcResult } from './rpc.ts'
 
 // ---- Method registry and derived generics ----