fix(folder-picker): address QoL issues from PR review

- Fix chevron tooltip: was "Open folder" in both branches; now shows
  "No subfolders" when the entry has no children (consistent with the
  existing opacity-45 visual cue on the same chevron icon)
- Fix Unix breadcrumb root label: was always "Home" even for non-home
  paths like /mnt/data — now labelled "/" which is always accurate
- Fix partial-failure staging: on a mixed add result, successfully-added
  entries are now removed from the staging panel so only genuinely failed
  folders remain for the user to retry (index-pairing is safe because the
  backend returns results in input order via a preserved .map())

src/components/FolderPickerModal.tsx

@@ -36,7 +36,7 @@ function buildBreadcrumbs(path: string | null): { label: string; path: string |
   const parts = normalized.split(/[\\/]+/).filter(Boolean);
   let current = separator === "/" ? "" : "";
   return [
-    { label: "Home", path: null },
+    { label: "/", path: null },
     ...parts.map((part) => {
       current = `${current}/${part}`;
       return { label: part, path: current };
@@ -117,7 +117,7 @@ function FolderRow({
         type="button"
         className="rounded-md p-1 text-gray-500 transition-colors hover:bg-white/[0.06] hover:text-white light-theme:hover:bg-gray-900 light-theme:hover:text-white"
         onClick={onNavigate}
-        title={entry.has_children ? "Open folder" : "Open folder"}
+        title={entry.has_children ? "Open folder" : "No subfolders"}
       >
         <svg className={`h-4 w-4 ${entry.has_children ? "" : "opacity-45"}`} fill="none" viewBox="0 0 24 24" stroke="currentColor">
           <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M9 5l7 7-7 7" />
@@ -300,6 +300,7 @@ export function FolderPickerModal() {
       const failed = addResults.filter((result) => result.status === "error");
       setResults(addResults);
       if (failed.length > 0) {
+        setStagedPaths(stagedPaths.filter((_, i) => addResults[i]?.status === "error"));
         setError(failed.map((failure) => failure.data).join("; "));
         return;
       }