Adds a "Download Folder" item to the workspace file-tree right-click
menu and a GET /api/folder/download endpoint that streams the
directory as a zip with Content-Disposition: attachment.
Configurable caps:
HERMES_WEBUI_FOLDER_ZIP_MAX_MB (default 1024)
HERMES_WEBUI_FOLDER_ZIP_MAX_FILES (default 50000)
Pre-flights the walk so cap-exceeded returns 413 + JSON BEFORE any
zip bytes are sent. Symlinks resolving outside the workspace are
skipped. Mirrors the existing _handle_file_raw shape (session_id
resolution, safe_resolve, RFC 5987 filename via
_content_disposition_value). Stdlib zipfile only; no new dependencies.
Tests: 11 static-inspection tests matching the style of
tests/test_issue1867_upload_size_preflight.py. All passing on
Python 3.11/3.12/3.13.
6caf86ba96