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 ----

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

@@ -50,6 +50,20 @@ export type RpcError = {
 /** Business success/failure result: the result slot of a unary response; methods never throw business errors. */
 export type RpcResult<T> = { ok: true; value: T } | { ok: false; error: RpcError }
 
+/**
+ * Fold a transport exception into the RpcResult error branch (unified error
+ * surface; 'internal' as the catch-all code). Lives with RpcResult so every
+ * carrier consumer folds the same way.
+ * @param error - the thrown value from the carrier.
+ * @returns the error branch of an RpcResult.
+ */
+export function transportError<T>(error: unknown): RpcResult<T> {
+  return {
+    ok: false,
+    error: { code: 'internal', message: error instanceof Error ? error.message : String(error), details: {} },
+  }
+}
+
 /**
  * Signature-layer narrow form, request side (domain-interface view, shared by
  * both directions): rpcId is explicit in the signature, never mixed into the