Calls of read run as threads of one process, so what one call writes
and collects is now kept apart from another's. A copy's working name
carries the thread as well as the process, so parallel reads of one
file each name the copy. What a conversion left behind is collected
from its own thread only, so concurrent conversions no longer take
each other's losses into the map and the metadata.

A path that names neither a folder nor a regular file is refused with
the reason, as a member of a folder is skipped, where before a FIFO
named directly left the call waiting. The description and README list
the refusal. _cache no longer repeats the relative-path rule _input
holds.

Require mcp 2.2, the SDK the server is built on.

Release 0.4.1 in pyproject.toml and server.json.