For GPT on the current runner surface, `ATTACHED:` may currently be:
- An http/https URL.
- A GPT sandbox path under /mnt/data/...

Do not emit `ATTACHED:` local-PC paths such as D:\\scratchpad\\abc.txt or D:\\kbos\\... on this surface.
For GPT sandbox publication, emit `ATTACHED:` paths only under /mnt/data/... on the active GPT container surface. Do not emit other Unix-style paths.
