S3 CloudFront Indexer v96 - Accessible sort headers

Purpose:
The generated Apache-style directory listing had sortable column headers named:

    Name
    Last modified
    Size

Those headers were technically clickable, but the text was too small to tap reliably on iPhone and iPad.

Change:
The Lambda@Edge directory browser now renders much larger sort buttons for those three table headers.
The visual style remains simple and Apache-like, but the touch target is intentionally larger.

Files changed:
    lambda-edge-directory-browser/index.mjs
    8k-art-directory-browser.txt

Deployment note:
To see this change on https://8k.art/beta/ directory pages, deploy the updated Lambda@Edge directory browser code, publish a new Lambda version, and update the CloudFront behavior association to that new version.

This does not change S3 updater behavior, CloudFront invalidation behavior, file sorting logic, or cache policy logic.