fix(host): native button semantics for rows; path editor inert under the create dialog

Rows keep their NATIVE button role inside a listitem seat (role overrides
exposed selectable folders as passive list items to assistive technology),
the crumb trail becomes a navigation landmark, and the path-edit input joins
the parentInert derivation so the nested create dialog cannot be undercut
through it.

packages/host/directory-picker-browse/src/client/DirectoryBrowser.module.css

@@ -140,7 +140,13 @@
   background: var(--dsw-alias-border-l3);
 }
 
+.rowSeat {
+  display: flex;
+  flex: none;
+}
+
 .row {
+  width: 100%;
   display: flex;
   align-items: center;
   gap: 4px;