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/src/api/commands.schema.ts

@@ -7,7 +7,7 @@ import { z } from 'zod'
 import type { RequestPayload, ResponseValue } from './rpc-map.ts'
 import type { Wire } from './rpc.schema.ts'
 import { sessionIdSchema } from './sessions.schema.ts'
-import type { CommandDescriptor, CommandExecuteResult } from './commands.ts'
+import type { CommandDescriptor } from './commands.ts'
 
 /** CommandDescriptor row of command.list. */
 export const commandDescriptorSchema = z.object({
@@ -32,14 +32,7 @@ export const commandExecuteRequestSchema = z.object({
   line: z.string(),
 }) satisfies z.ZodType<Wire<RequestPayload<'command.execute'>>>
 
-/** Detached command outcome (result slot of command.execute's value). */
-export const commandExecuteResultSchema = z.object({
-  kind: z.union([z.literal('success'), z.literal('error')]),
-  text: z.string().optional(),
-}) satisfies z.ZodType<Wire<CommandExecuteResult>>
-
-/** command.execute response value (matched=false carries no result). */
+/** command.execute response value: pure admission — outcomes ride the logged lifecycle events, never this response. */
 export const commandExecuteValueSchema = z.object({
   matched: z.boolean(),
-  result: commandExecuteResultSchema.optional(),
 }) satisfies z.ZodType<Wire<ResponseValue<'command.execute'>>>

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

@@ -22,12 +22,6 @@ export interface CommandDescriptor {
   readonly input?: { readonly hint: string }
 }
 
-/** Detached command outcome rendered directly by the requesting client. */
-export interface CommandExecuteResult {
-  readonly kind: 'success' | 'error'
-  readonly text?: string
-}
-
 /** Command-domain unary methods (the map keys command.* of RpcMethodMap). */
 export interface CommandsApi {
   /**
@@ -38,11 +32,14 @@ export interface CommandsApi {
 
   /**
    * Parses and executes one slash-command line against the addressed agent
-   * without sending it to the model. matched=false when syntax or name does
-   * not resolve (the client falls back to its default sink). The signal rides
-   * beside the request, never on the wire: the fetch carrier's request signal
-   * cancels the running handler.
+   * without sending it to the model — pure admission semantics. matched=false
+   * when syntax or name does not resolve (the client falls back to its
+   * default sink). The handler's outcome does NOT ride the response: the host
+   * executor durably logs the lifecycle (`command/run`/`command/done`), which
+   * broadcasts on the mux stream and renders as a persistent flow node. The
+   * signal rides beside the request, never on the wire: the fetch carrier's
+   * request signal cancels the running handler.
    */
   execute(request: RpcRequest<{ sessionId: SessionId; line: string }>, signal: AbortSignal):
-  Promise<RpcResponse<{ matched: boolean; result?: CommandExecuteResult }>>
+  Promise<RpcResponse<{ matched: boolean }>>
 }

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

@@ -28,7 +28,7 @@ export interface ApiProxy {
 export type { HistoryEntry, SessionProjectionsBlock, SessionsApi, SessionSummary } from './sessions.ts'
 export type { HostApi } from './host.ts'
 export type { WorkspaceApi, WorkspaceId, WorkspaceView } from './workspace.ts'
-export type { CommandsApi, CommandDescriptor, CommandExecuteResult } from './commands.ts'
+export type { CommandsApi, CommandDescriptor } from './commands.ts'
 export type { SkillsApi, SkillEntry } from './skills.ts'
 export type { EventsApi, MuxFrame, HostFrame, ToolCallView, ToolEventView, ToolResultView } from './events.ts'
 export type { ApprovalResponsePayload } from './approvals.ts'