bug(fmt): when using `/dev/mem` it stopped before the end of the file

Hi, uutils mainteners

we confirmed when the filename is /dev/mem

the uu fmt

stops at

qPZ 8(-

while the gnu fmt stops at

qPZ 8(- dpaPR


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gnufmt: read error

there was a truncation in the uu one it do not completed until the end of the file, stopped early

Start by locating the Rust implementation and tests for the fmt command, then reproduce the behavior with /dev/mem and compare it with GNU fmt. Trace why uu fmt stops before EOF; done means it processes the input through the end of the file without the observed premature truncation.