Behavior-contract tests for sanitize_task_id_for_path (colon/separator
removal, verbatim pass-through for existing safe ids, determinism,
collision-freedom incl. the a:b vs a_b digest case, traversal and
oversized-id bounds) and for the singularity persistent overlay path
(sanitized, verbatim for safe ids, distinct dirs for colon-vs-underscore
ids).
Co-authored-by: chelsealong <chelsealong@126.com>
Co-authored-by: Parker Fawcett <259203091+Parker-Fawcett@users.noreply.github.com>