fix(host): address review — Escape scoping, relist gating, crumb overflow, aria golden

- Escape (and the mask) now reaches only the topmost dialog: while the
  nested New-folder dialog is up the browser ignores its own Modal close,
  and the nested dialog's in-flight fence keeps both open during creation.
- New folder disables while any listing loads, so a slow post-create
  relist/select sequence cannot host a second create against a target the
  pending listing is about to change.
- Deep ancestry scrolls inside a dedicated crumb trail whose tail is pinned
  into view; the path-edit zone keeps its reserved width instead of being
  clipped by the card, preserving cross-drive path entry.
- The workspace-management e2e records a directory-browser aria golden at a
  staged tree (host HOME pointed at the scaffold cwd collapses ancestry into
  the Home crumb, keeping the artifact machine-independent), and the keyless
  snapshot's row targeting goes through visible label text — listitem
  accessible-name computation differs across dom-accessibility-api
  environments (the CI-only miss).

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

@@ -39,6 +39,18 @@
   min-height: 20px;
 }
 
+/* Deep chains scroll inside the trail (the effect pins the tail into view)
+ * so the edit zone to the right never leaves the bar. */
+.crumbTrail {
+  display: flex;
+  align-items: center;
+  gap: 4px;
+  flex: 0 1 auto;
+  min-width: 0;
+  overflow-x: auto;
+  scrollbar-width: none;
+}
+
 .crumbSeat {
   display: inline-flex;
   align-items: center;
@@ -74,7 +86,7 @@
 /* The empty remainder of the bar: invisible, but a real click target that
  * flips the bar into path-edit mode. */
 .crumbEditZone {
-  flex: 1 1 0;
+  flex: 1 0 34px;
   min-width: 34px;
   align-self: stretch;
   border: none;