refactor: command.execute degrades to pure admission; composer notice channel retired

The wire response now carries only the matched bit — CommandExecuteResult
is deleted from the api, schema, and client mirrors (pre-release, no shim);
outcomes ride the durably logged command/run/command/done pair broadcast on
the mux stream and render as flow nodes. ui-command's runDetached→noticeFor
outcome routing is retired: admitted commands surface nothing through the
composer, while admission misses (matched:false, syntax feedback) and
transport failures keep their immediate notice. The connection fixture
mirrors the host: an admitted command appends the lifecycle pair to the
session log instead of returning result text.

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

@@ -2,7 +2,7 @@
 // data source on a real clock; behavior tests need per-case responses and
 // deferred-controlled timing). Streams are hand pumps: pushMux/pushHost.
 import type {
-  CommandDescriptor, CommandExecuteResult, HostFrame, IApiClient, MuxFrame,
+  CommandDescriptor, HostFrame, IApiClient, MuxFrame,
   RpcRequest, RpcResponse, SessionId, SkillEntry,
 } from '../src/client/api.ts'
 import { RpcId } from '../src/client/api.ts'
@@ -94,7 +94,7 @@ export class FakeApiClient implements IApiClient {
   // wire shapes so cases can program catalogs and skill lists without casts.
   onCommandList: (payload: unknown) => Promise<RpcResponse<{ commands: CommandDescriptor[] }>>
     = () => Promise.resolve(ok({ commands: [] }))
-  onCommandExecute: (payload: unknown) => Promise<RpcResponse<{ matched: boolean; result?: CommandExecuteResult }>>
+  onCommandExecute: (payload: unknown) => Promise<RpcResponse<{ matched: boolean }>>
     = () => Promise.resolve(ok({ matched: false }))
   onSkillList: (payload: unknown) => Promise<RpcResponse<{ skills: SkillEntry[] }>>
     = () => Promise.resolve(ok({ skills: [] }))