fix(files): name single-folder downloads after the folder

The File Browser's selected-files download flow zips any selection
that is not a single file and always applies the generic
agent-zero-selected-<count>-<stamp>.zip archive name, so downloading
one folder produced agent-zero-selected-1-<date>-<time>.zip instead
of <folder>.zip.

Name single-directory downloads after the folder in both the local and
remote branches of prepare_files_download; true multi-selections keep
the timestamped generic name. Add regression tests for both cases.

helpers/file_browser.py

@@ -532,7 +532,9 @@ def prepare_files_download(paths, current_path=""):
         except BaseException:
             Path(path).unlink(missing_ok=True)
             raise
-        name = posixpath.basename(paths[0]) if single else selected_archive_name(len(paths))
+        name = posixpath.basename(paths[0]) if single else (
+            f"{posixpath.basename(paths[0])}.zip" if len(paths) == 1 else selected_archive_name(len(paths))
+        )
         temporary = True
     elif len(paths) == 1 and Path(paths[0]).is_file():
         import stat
@@ -557,7 +559,10 @@ def prepare_files_download(paths, current_path=""):
         temporary = True
     else:
         path = create_selected_zip(paths, current_path, limit, FileBrowser.max_archive_entries())
-        name = selected_archive_name(len(paths))
+        name = (
+            f"{Path(paths[0]).name}.zip" if len(paths) == 1
+            else selected_archive_name(len(paths))
+        )
         temporary = True
     return {"file_source": path, "download_name": name, "max_bytes": limit, "delete_after": temporary}
 

helpers/file_browser.py.dox.md

@@ -58,7 +58,7 @@
 
 No child DOX files.
 
-`read_text` owns bounded local Editor reads. `encode_upload` bounds the development RFC adapter. `prepare_files_download` owns Files routing and policy; `register_files_download` rechecks remote permission at delivery. API handlers do not select byte limits. Generic attachment/Connector downloads remain separate.
+`read_text` owns bounded local Editor reads. `encode_upload` bounds the development RFC adapter. `prepare_files_download` owns Files routing and policy; a single selected directory downloads as `<folder>.zip` while true multi-selections keep the timestamped `agent-zero-selected-<count>-<stamp>.zip` archive name. `register_files_download` rechecks remote permission at delivery. API handlers do not select byte limits. Generic attachment/Connector downloads remain separate.
 
 Destructive entry operations resolve parent directories while preserving the final symlink. Delete/Rename operate on the link itself; empty/root targets are rejected in the shared helper. Local Files downloads stage a bounded snapshot and reject in-place source changes during preparation. Cancelled preparation closes late responses and their temporary descriptors.
 

tests/test_download_folder_naming.py

@@ -0,0 +1,34 @@
+from pathlib import Path
+import zipfile
+
+from helpers.file_browser import prepare_files_download
+
+
+def test_single_folder_download_is_named_after_the_folder(tmp_path: Path) -> None:
+    folder = tmp_path / "my-folder"
+    folder.mkdir()
+    (folder / "file.txt").write_text("content", encoding="utf-8")
+
+    # A single selected folder downloads as <folder>.zip, not the generic
+    # agent-zero-selected-<count>-<stamp>.zip archive name.
+    download = prepare_files_download([str(folder)], current_path=str(tmp_path))
+    try:
+        assert download["download_name"] == "my-folder.zip"
+        assert zipfile.is_zipfile(download["file_source"])
+    finally:
+        Path(download["file_source"]).unlink(missing_ok=True)
+
+
+def test_multi_selection_download_keeps_generic_archive_name(tmp_path: Path) -> None:
+    one = tmp_path / "one.txt"
+    two = tmp_path / "two.txt"
+    one.write_text("1", encoding="utf-8")
+    two.write_text("2", encoding="utf-8")
+
+    download = prepare_files_download([str(one), str(two)], current_path=str(tmp_path))
+    try:
+        # True multi-selections keep the timestamped generic archive name.
+        assert download["download_name"].startswith("agent-zero-selected-2-")
+        assert download["download_name"].endswith(".zip")
+    finally:
+        Path(download["file_source"]).unlink(missing_ok=True)