zddc-server can now hand back a whole directory subtree as a single
streamed application/zip download: GET /some/dir/?zip=1 (works on both
/dir and /dir/) → Content-Type: application/zip + Content-Disposition:
attachment; filename="<dir>.zip", containing every readable file under
/some/dir/, recursively.
handler.ServeSubtreeZip walks the tree with filepath.WalkDir, ACL-gates
each file by the .zddc chain of its containing directory (per-dir
decision cache, same shape as serveArchiveListing), skips hidden
entries ("." and "_" prefixes — .zddc, _template, _app), and adds a
.zip *file* it encounters as opaque bytes (it does not recurse into it
— that's the navigable-virtual-surface feature, a different thing).
The response is streamed (zip.NewWriter straight onto the
ResponseWriter, Store for already-compressed extensions, Deflate
otherwise), so a fully-ACL-denied or empty subtree just yields a valid
empty zip rather than a 403 (a stream can't change status after the
headers go out; empty leaks no more than 403). HEAD sends the headers
and no body. The dispatch's directory ACL gate still runs first, so a
viewer who can't read the directory gets 403 before the handler.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
