refactor: brand the command lifecycle pairing id as CommandId

commandId crosses three boundaries (session log, wire admission response,
client flow pairing), so per the branded-id rule it becomes
Branded<'CommandId'>, declared in a new pure @deepseek-ai/dsh-commands/brand
outlet (the dsh-llm/brand shape: type + constructor, no Context merges, so
wire and client programs can name it without loading the host plugin). The
event payloads, CommandExecution, and the executor mint carry the brand; the
wire schema gains commandIdSchema as the domain's single brand-cast point
(the approvals precedent); CommandNode and the fixture's fabrication cast
follow type-only.

packages/host/apiproxy/src/api/commands.schema.ts

@@ -4,6 +4,7 @@
  */
 
 import { z } from 'zod'
+import type { CommandId } from '@deepseek-ai/dsh-commands/brand'
 import type { RequestPayload, ResponseValue } from './rpc-map.ts'
 import type { Wire } from './rpc.schema.ts'
 import { sessionIdSchema } from './sessions.schema.ts'
@@ -32,8 +33,11 @@ export const commandExecuteRequestSchema = z.object({
   line: z.string(),
 }) satisfies z.ZodType<Wire<RequestPayload<'command.execute'>>>
 
+/** CommandId: one brand cast after shape validation (the only cast point in this domain). */
+export const commandIdSchema = z.string().min(1) as unknown as z.ZodType<CommandId>
+
 /** command.execute response value: pure admission — outcomes ride the logged lifecycle events; commandId (present exactly when matched) correlates with them. */
 export const commandExecuteValueSchema = z.object({
   matched: z.boolean(),
-  commandId: z.string().min(1).optional(),
+  commandId: commandIdSchema.optional(),
 }) satisfies z.ZodType<Wire<ResponseValue<'command.execute'>>>

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

@@ -5,6 +5,7 @@
  * together), so there is no agent-less surface on this wire.
  */
 
+import type { CommandId } from '@deepseek-ai/dsh-commands/brand'
 import type { SessionId } from '@deepseek-ai/dsh-session/types'
 import type { RpcRequest, RpcResponse } from './rpc.ts'
 
@@ -43,5 +44,5 @@ export interface CommandsApi {
    * wire: the fetch carrier's request signal cancels the running handler.
    */
   execute(request: RpcRequest<{ sessionId: SessionId; line: string }>, signal: AbortSignal):
-  Promise<RpcResponse<{ matched: boolean; commandId?: string }>>
+  Promise<RpcResponse<{ matched: boolean; commandId?: CommandId }>>
 }

packages/host/apiproxy/tests/fetch-carrier.spec.ts

@@ -1,3 +1,4 @@
+import { CommandId } from '@deepseek-ai/dsh-commands/brand'
 import { describe, expect, it, vi } from 'vitest'
 import type { ApiProxy, HostFrame, MuxFrame } from '../src/api/index.ts'
 import type { ClientResponse, RpcMessage, RpcReceipt, RpcRequest } from '../src/api/rpc.ts'
@@ -91,7 +92,7 @@ function fakeApi(overrides: Partial<{ muxFrames: MuxFrame[]; hostFrames: HostFra
           return { rpcId: request.rpcId, result: { ok: false, error: { code: 'cancelled', message: 'aborted', details: {} } } }
         }
         if (request.payload.line.startsWith('/plan')) {
-          return { rpcId: request.rpcId, result: { ok: true, value: { matched: true, commandId: 'cmd-x' } } }
+          return { rpcId: request.rpcId, result: { ok: true, value: { matched: true, commandId: CommandId('cmd-x') } } }
         }
         return { rpcId: request.rpcId, result: { ok: true, value: { matched: false } } }
       },