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.

apps/web/tests/workspace-flow.snapshot.ts

@@ -37,6 +37,15 @@ const PLUGINS: readonly (WebBootEntry & { dir: string })[] = [
     ],
   },
   { id: '@deepseek-ai/dsh-client-ui-trajectory', dir: 'ui-trajectory', url: '/plugins/ui-trajectory.js', rev: 'fx', inject: ['@deepseek-ai/dsh-client-ui-conversation'] },
+  // Dual-face host package: its browser half fills the directory-flow holes
+  // (the same composition row apps/cli mounts for the node-side backend).
+  {
+    id: '@deepseek-ai/dsh-host-directory-picker-native',
+    dir: '../host/directory-picker-native',
+    url: '/plugins/directory-picker-native.js',
+    rev: 'fx',
+    inject: ['@deepseek-ai/dsh-client-runtime', '@deepseek-ai/dsh-client-ui-workspace'],
+  },
 ]
 
 const bundles = new Map(PLUGINS.map(plugin => [
@@ -174,18 +183,24 @@ it('locks the composer in the New Session view state until a Workspace is chosen
   `)
 })
 
-it('hides the Open-local-folder entry under the fixture host\'s browse picker capability', async () => {
+it('adopts a directory through the composed native flow and lands in its blank session', async () => {
   boot('?fixture=empty')
 
   await findLockedComposer()
   fireEvent.click(workspaceChip())
   const menu = await screen.findByRole('menu')
-  // Flush the advertised-kind read (fixture describe resolves in microtasks):
-  // the fixture serves `browse`, whose in-app UI is not wired yet, so the
-  // dialog affordance must not render — only the create action remains.
-  await act(async () => {})
+  // The composed flow package occupies the directory-flow hole, so the
+  // picking affordance is present (no advertised-kind read exists anymore).
   expect(within(menu).getAllByRole('menuitem').map(item => visibleText(item)))
-    .toEqual(['Create a new workspace'])
+    .toEqual(['Open local folder…', 'Create a new workspace'])
+  fireEvent.click(within(menu).getByRole('menuitem', { name: 'Open local folder…' }))
+  // The renderless native flow drives the fixture's deterministic pick and
+  // the owner adopts the returned path into a real Workspace.
+  await act(async () => {})
+  await findHeroComposer()
+  await waitFor(() => {
+    expect(visibleText(screen.getByRole('tree', { name: 'Sessions' }))).toContain('project')
+  })
 })
 
 it('selects the recent Workspace and opens its blank Session on first load', async () => {