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/host/apiproxy/tests/api-proxy-commands.spec.ts

@@ -115,8 +115,15 @@ describe('command.execute', () => {
     const api = createApiProxy(ctx, DEFAULTS)
     const agent = stubAgent(ctx)
     const value = expectOk(await api.commands.execute(request({ sessionId: agent.id, line: '/goal ship it' }), new AbortController().signal))
-    expect(value).toEqual({ matched: true, result: { kind: 'success', text: `goal:${agent.id}` } })
+    expect(value).toEqual({ matched: true })
     expect(received).toBe(' ship it')
+    // Pure admission on the wire: the outcome rides the durably logged
+    // lifecycle pair instead of the response.
+    const lifecycle = agent.session.events.filter(e => e.type === 'command/run' || e.type === 'command/done')
+    expect(lifecycle).toMatchObject([
+      { type: 'command/run', data: { name: 'goal', line: '/goal ship it' } },
+      { type: 'command/done', data: { kind: 'success', text: `goal:${agent.id}` } },
+    ])
   })
 
   it('returns matched:false when syntax or name does not resolve', async () => {