feat(host,client): compose directory picking through slots — dual-face -native, no wire advertisement

ui-workspace's two trigger surfaces each declare a single-kind directory-flow
hole (conversation.hero.workspace.directoryFlow / sidebar.workspaces.directoryFlow,
same owner contract) and keep only the trigger and the adoption: the Open-local-
folder entry renders while the surface's hole is occupied, and the occupant
reports one picked path per open through the hole's owner conversation
(open/busy/onPicked/onCancel/onError).

directory-picker-native becomes dual-face: its browser half fills both holes
with a renderless occupant driving host.pickDirectory, so the cordis.yml row
that mounts the backend also composes the client interaction — a mismatch is
impossible and a second flow package fails at client load.

With composition wiring both sides, the host.describe.directoryPicker
advertisement and the client's kind branching lose their last consumer:
the field, WorkspacesService.directoryPickerKind(), the DirectoryPickerKind
wire type, and the picker's per-open describe read are deleted. The connection
fixture now serves a deterministic pickDirectory path so the keyless snapshot
drives the full pick-then-adopt flow. ui-workspace's hand-rolled declaration
deferral is replaced by the deferRegistration helper it duplicated.

packages/client/runtime/src/client/index.ts

@@ -23,7 +23,7 @@ export type { SessionListPhase } from './sessions/manager.ts'
 export type { WorkspaceListPhase } from './workspaces/manager.ts'
 export type { WorkspaceListState } from './workspaces/service.ts'
 export type {
-  DirectoryEntry, DirectoryListing, DirectoryPickerKind, WorkspaceId, WorkspaceView,
+  DirectoryEntry, DirectoryListing, WorkspaceId, WorkspaceView,
 } from '@deepseek-ai/dsh-client-connection/client'
 // Runtime owns the snapshot store; web-react only binds it to React.
 export { createSnapshotStore, defineStore, shallowEqual } from './contract/store.ts'

packages/client/runtime/src/client/workspaces/service.ts

@@ -2,7 +2,7 @@
 
 import type { Context } from 'cordis'
 import type {
-  DirectoryListing, DirectoryPickerKind, IApiClient, RpcError,
+  DirectoryListing, IApiClient, RpcError,
   SessionId, WorkspaceId, WorkspaceView,
 } from '@deepseek-ai/dsh-client-connection/client'
 import type { SnapshotStore } from '../contract/store.ts'
@@ -191,21 +191,6 @@ export class WorkspacesService {
     return response.result.value.path
   }
 
-  /**
-   * The directory-picking interaction the Host composed — the fact the picker
-   * UI branches on (`native` opens the native chooser; `browse` opens the
-   * in-app browser). Read per flow open: one describe round trip, no cache to
-   * go stale across reconnects.
-   * @returns the Host's advertised picker kind.
-   */
-  async directoryPickerKind(): Promise<DirectoryPickerKind> {
-    const response = await this.api.host.describe({})
-    if (!response.result.ok) {
-      throw new Error(`host describe failed: ${response.result.error.message}`)
-    }
-    return response.result.value.directoryPicker
-  }
-
   /**
    * List one directory level through the Host's `browse` capability.
    * @param path - absolute directory to list; absent lists the Host home directory.

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

@@ -81,8 +81,8 @@ export class FakeApiClient implements IApiClient {
     payload => Promise.resolve(ok({ selected: { provider: payload.provider, model: payload.model } }))
   onPrompt: (payload: unknown) => Promise<RpcResponse<{ accepted: true }>> = () => Promise.resolve(ok({ accepted: true as const }))
   onCancel: (payload: unknown) => Promise<RpcResponse<{ accepted: true }>> = () => Promise.resolve(ok({ accepted: true as const }))
-  onDescribe: (payload: unknown) => Promise<RpcResponse<{ version: string; cwd: string; attachedSessions: number; directoryPicker: 'native' | 'browse' }>> =
-    () => Promise.resolve(ok({ version: '0-fake', cwd: '/f', attachedSessions: 0, directoryPicker: 'browse' as const }))
+  onDescribe: (payload: unknown) => Promise<RpcResponse<{ version: string; cwd: string; attachedSessions: number }>> =
+    () => Promise.resolve(ok({ version: '0-fake', cwd: '/f', attachedSessions: 0 }))
   onPickDirectory: (payload: unknown) => Promise<RpcResponse<{ path: string | null }>> =
     () => Promise.resolve(ok({ path: null }))
   onOpenPath: (payload: unknown) => Promise<RpcResponse<{ opened: true }>> =

packages/client/runtime/tests/workspaces-service.spec.ts

@@ -238,15 +238,6 @@ describe('WorkspacesService', () => {
     await expect(workspaces.pickDirectory()).rejects.toThrow(/no chooser/)
   })
 
-  it('reads the picker kind from describe per call, failing loud on an unreachable host', async () => {
-    const ctx = new Context()
-    const api = new FakeApiClient()
-    const workspaces = new WorkspacesService(ctx, api, new SessionsService(ctx, api))
-    await expect(workspaces.directoryPickerKind()).resolves.toBe('browse')
-    api.onDescribe = () => Promise.resolve(err({ code: 'internal', message: 'down', details: {} }))
-    await expect(workspaces.directoryPickerKind()).rejects.toThrow(/host describe failed/)
-  })
-
   it('passes listings and creation through the browse wire, wrapping business failures', async () => {
     const ctx = new Context()
     const api = new FakeApiClient()