logs should capture stderr

We ran into an issue where cardano-node.exe wouldn't start because of a missing dll but log had no errors in it. Had to run manually on CLI to get the error because launcher doesn't capture stderr. WOuld ease debugging of end user issues if we captured stderr in additon to stdout.

Start at the launcher code that starts cardano-node.exe and handles its stdout, then trace how command-line errors are written to logs. Ensure stderr is captured alongside stdout, and verify that a missing-DLL startup failure appears in the launcher log.

Written by the indexing model from the issue text.