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/host/apiproxy/src/api-proxy.ts

@@ -67,7 +67,7 @@ import type {} from '@deepseek-ai/dsh-session-projection-cache'
 // GoalError narrows domain rejections to their stable codes at the wire boundary.
 import { GoalError } from '@deepseek-ai/dsh-goal'
 import type { GoalRef as CoreGoalRef } from '@deepseek-ai/dsh-goal'
-// Type-only edges: resolve `ctx.get('commands')`, the `commands/change` event, and `ctx.get('skills')`.
+// Type-only edges: resolve the command-change stream and `ctx.get('skills')`.
 import type {} from '@deepseek-ai/dsh-commands'
 import type {} from '@deepseek-ai/dsh-skill'
 // The settings/credentials seams: brand guards run at this wire boundary; the
@@ -2889,49 +2889,6 @@ export function createApiProxy(ctx: Context, defaults: ApiProxyDefaults): ApiPro
       },
     },
 
-    commands: {
-      // Both methods address one session's agent. agentFor resumes on miss
-      // and fences every subagent-owned identity with `agent-busy`; the
-      // api/commands.ts module contract owns that fence's wording, so this
-      // comment only notes the routing shape: clients send a sessionId for a
-      // published session, and resume restores an existing entity.
-      async list(request) {
-        // Missing service = the deployment omitted dsh-commands from its
-        // composition, not an empty catalog: fail loud instead of serving [].
-        const commands = ctx.get('commands')
-        if (commands === undefined) {
-          return err(request, { code: 'internal', message: 'command registry is absent: this deployment does not mount @deepseek-ai/dsh-commands in its composition (cordis.yml or explicit assembly)', details: {} })
-        }
-        const found = await agentFor(request.payload.sessionId)
-        if ('error' in found) return err(request, found.error)
-        return ok(request, { commands: commands.list(found.agent) })
-      },
-
-      async execute(request, signal) {
-        const commands = ctx.get('commands')
-        if (commands === undefined) {
-          return err(request, { code: 'internal', message: 'command registry is absent: this deployment does not mount @deepseek-ai/dsh-commands in its composition (cordis.yml or explicit assembly)', details: {} })
-        }
-        const { sessionId, line } = request.payload
-        const found = await agentFor(sessionId)
-        if ('error' in found) return err(request, found.error)
-        try {
-          // Pure admission: the executor's durable command/run + command/done
-          // pair (broadcast on the mux stream) carries the outcome; the
-          // response reports whether the line resolved to a handler, plus the
-          // minted pairing id so the issuing client can correlate its request
-          // with the flow node the lifecycle events produce.
-          const execution = await commands.execute(found.agent, line, signal)
-          return ok(request, execution === undefined
-            ? { matched: false }
-            : { matched: true, commandId: execution.commandId })
-        } catch (error: unknown) {
-          if (signal.aborted) return err(request, { code: 'cancelled', message: 'command execution was aborted', details: {} })
-          return err(request, { code: 'internal', message: `command failed: ${String(error)}`, details: {} })
-        }
-      },
-    },
-
     goals: {
       // Mutations only — the read side is the 'goal' session projection.
       // Every verb resolves the session's agent (agentFor: implicit cold