[Larrtroffen]

Problem

Archive preview drops every sub-directory for zips that do not contain explicit directory entries — which is what python -m zipfile, Python's zipfile module and many CI packers produce (only file entries such as task/environment/Dockerfile).

For a 157-file archive with 10 top-level folders:

• POST /api/fs/archive/meta returns only the files that sit directly in the first path segment; folders are missing.
• POST /api/fs/archive/list with inner_path=/<top-folder> returns only those same files, so the folders can never be reached from the UI.

Zips with explicit directory entries happen to work, which makes it look like a frontend issue.

Root cause

1. internal/archive/tool/helper.go, GenerateMetaTreeFromFolderTraversal: when a new folder chain is created and an ancestor already exists in dirMap, the loop appends the child to its parent but breaks before attaching the newly created parent to the existing grandparent. The intermediate folder becomes an orphan.

   Minimal case: a/ exists (from a/README.txt), then a/b/c/file.txt arrives: b is created and c appended to it, but b is never appended to a.

2. internal/archive/zip/zip.go, (*Zip).List: only looks at entries whose dirname equals inner_path; deeper paths are skipped and no intermediate directories are synthesized.

Fix

• Attach every newly created ancestor until an existing node is reached (and never attach the root to itself).
• In Zip.List, match entries by inner_path + "/" prefix, and turn the next path segment into a synthesized folder object when the remainder still contains /.
• Add internal/archive/tool/helper_tree_test.go covering a zip with no directory records.

Verification

import zipfile
with zipfile.ZipFile('t.zip', 'w') as z:
    z.writestr('proj/README.txt', 'x')
    z.writestr('proj/sub/deep/file.txt', 'y')  # no directory entries

Before: proj/sub missing. After: proj/sub/deep/file.txt reachable; go test ./internal/archive/... passes.