refactor(commands): move the command service to Remote

`CommandService.list` and `execute` carry the wire contract directly through
`@Remote`, and the Client assembly mounts the generated commands
contribution. The legacy API Proxy route, its schemas, the map rows, the
generated client methods and the fixture's command domain are removed, so the
catalog and the admission call have one owner again.

`Session.command()` keeps a result-shaped public face for parity with the
prompt, cancel and attachment neighbours it sits beside, and reads the
generated namespace through one `SessionRemotes` parameter. The Session
cluster declares that face against the owning business package rather than the
generated contribution: the Host compiler aggregate builds this package, and
it runs before any contribution is emitted.

Migrated calls lose the `title-invalid` class of protocol-only error codes and
report `internal`; no production caller branched on them.

packages/client/runtime/tests/fake-api.ts

@@ -1,13 +1,13 @@
 // Test-local programmable IApiClient fake (NOT the fixture: fixture is a demo
 // data source on a real clock; behavior tests need per-case responses and
 // deferred-controlled timing). Streams are hand pumps: pushMux/pushHost.
-import type { CommandId } from '@deepseek-ai/dsh-commands/brand'
 import type {
-  ClientResponse, CommandDescriptor, HostFrame, IApiClient, ModelSelection, MuxFrame,
+  ClientResponse, HostFrame, IApiClient, ModelSelection, MuxFrame,
   RpcError, RpcReceipt, RpcRequest, RpcResponse, SessionId, SessionModels, SessionSearchItem, SkillEntry,
   WorkspaceId, WorkspaceView,
-} from '@deepseek-ai/dsh-client-connection/client'
+} from '@deepseek-ai/dsh-api-remotes/client'
 import { RpcId } from '@deepseek-ai/dsh-client-connection/client'
+import type { SessionRemotes } from '../src/client/sessions/remotes.ts'
 
 /** Programmable-default workspace row (branded id, ISO-ish times). */
 function fakeWorkspace(id: string, over: Partial<WorkspaceView> = {}): WorkspaceView {
@@ -55,6 +55,20 @@ interface StreamConn<F> {
   feed(item: StreamItem<F>): void
 }
 
+/**
+ * Commands Remote double: the generated face delivers the carrier's outcome, so
+ * a test that programs nothing sees an empty catalog and an unmatched line.
+ * @returns the Remote namespaces the session cluster calls.
+ */
+export function fakeRemote(): SessionRemotes {
+  return {
+    commands: {
+      list: () => Promise.resolve({ ok: true, value: [] }),
+      execute: () => Promise.resolve({ ok: true, value: undefined }),
+    },
+  }
+}
+
 export class FakeApiClient implements IApiClient {
   /** Chronological call record: [method, payload]. */
   readonly calls: { method: string; payload: unknown }[] = []
@@ -205,19 +219,10 @@ export class FakeApiClient implements IApiClient {
   // Payloads stay `unknown` (lint-lane note above); response rows are the real
   // wire shapes so cases can program requires-bearing catalogs and dual-address
   // skill lists without casts.
-  onCommandList: (payload: unknown) => Promise<RpcResponse<{ commands: CommandDescriptor[] }>>
-    = () => Promise.resolve(ok({ commands: [] }))
-  onCommandExecute: (payload: unknown) => Promise<RpcResponse<{ matched: boolean; commandId?: CommandId }>>
-    = () => Promise.resolve(ok({ matched: false }))
   onSkillList: (payload: unknown) => Promise<RpcResponse<{ skills: SkillEntry[] }>>
     = () => Promise.resolve(ok({ skills: [] }))
 
 
-  readonly commands: IApiClient['commands'] = {
-    list: (payload: unknown) => this.record('command.list', payload, this.onCommandList(payload)),
-    execute: (payload: unknown) => this.record('command.execute', payload, this.onCommandExecute(payload)),
-  }
-
   readonly agentPresets: IApiClient['agentPresets'] = {
     list: (payload: unknown) => this.record('agentPreset.list', payload, Promise.resolve(ok({ presets: [], authorable: false, hasDocument: false }))),
     select: (payload: { agentPreset: string }) =>