fix(cli): diagnose an INI overlay passed to --overlay

The INI overlay form is a SOURCE format that 'colitur convert' turns into
the S-expression one. Handing the INI to --overlay instead failed deep in
the sexp reader with 'more than one S-expression in file', which names
neither the cause nor the cure -- and the shipped examples under
data/ef/examples/ are exactly the files someone would try that with.

The detector reads past the comment header to the first real line and
looks for a [section]. Its first version capped that scan at 40 lines and
poland.ini's own header is 43, so it silently never fired on the very
file it was written for; the cap now bounds only how much of a binary
gets read, and is not a guess at header length.

0 files changed, 0 insertions, 0 deletions