fetch downloads each file to a temp name beside it and first removes
whatever is there. A manifest listing both a.txt and .a.txt.tmp had
fetch delete the second while fetching the first, then exit 0 with a
tree check rejects.
The refusal of a manifest that lists the saved manifest's own name or
temp name now covers this too: a listed file, or a directory a listed
file is in, may not sit at any name fetch writes besides the listed
files themselves. Temp names come from tempPathFor, names are compared
ignoring case as before, and the refusal still happens before the
destination is created or any file requested.
Model: opus-5-5
sneak