fix(client,host): review round — hooks-compartment occupancy, StrictMode re-arm, internal flow module, honest swap comment

- Directory-flow occupancy moves onto the inject face's reserved hooks
  compartment: apply publishes a stable observable per surface and the
  renderer binds useDirectoryFlow — no hand-rolled component subscriptions
  (the client contract's channel for registrant-private reactive facts).
- The native flow's alive guard re-arms in effect setup: StrictMode's
  development replay ran the cleanup once and every later outcome was
  discarded.
- NativeDirectoryFlow moves to a package-internal module; ./client exports
  only the Loader surface, tests import the internal module directly.
- The composition swap comment no longer advertises -browse as a complete
  swap before its dialog lands (stacked follow-up).

packages/client/ui-workspace/src/client/WorkspaceBrowser.tsx

@@ -253,8 +253,7 @@ export function WorkspaceBrowser({
   deleteWorkspace,
   insertSessionBefore,
   createWorkspace,
-  hasDirectoryFlow,
-  subscribeDirectoryFlow,
+  useDirectoryFlow,
   renderSlot,
 }: WorkspaceBrowserProps) {
   const workspaces = useWorkspaces(state => state.items)
@@ -373,8 +372,7 @@ export function WorkspaceBrowser({
           anchorRef={wsPlusRef}
           useWorkspaces={useWorkspaces}
           createWorkspace={createWorkspace}
-          hasDirectoryFlow={hasDirectoryFlow}
-          subscribeDirectoryFlow={subscribeDirectoryFlow}
+          useDirectoryFlow={useDirectoryFlow}
           renderDirectoryFlow={owner => renderSlot('sidebar.workspaces.directoryFlow', owner)}
           createOnly
           side="right"