runner: humanize ffprobe errors

[emranemran]

A close inspection of ffprobe errors now indicates almost all ffprobe failures are related to invalid input.

[codecov]

Codecov Report

Merging #152 (c6baa62) into main (1a1eefe) will not change coverage.
The diff coverage is 100.00000%.

@@              Coverage Diff              @@
##                main        #152   +/-   ##
=============================================
  Coverage   11.01695%   11.01695%           
=============================================
  Files             14          14           
  Lines           2124        2124           
=============================================
  Hits             234         234           
  Misses          1873        1873           
  Partials          17          17           

Impacted Files	Coverage Δ
task/runner.go	18.18182% <100.00000%> (ø)

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Impacted Files	Coverage Δ
task/runner.go	18.18182% <100.00000%> (ø)