- logging: LogToFile shadowed the package-level fileLogger, so
IsFileLogger was always false and Shutdown never closed the file
- logging: replace IsJSONHandler's unsafe reflection into slog
internals with a *slog.JSONHandler type check
- cli: fail if the log file can't be opened instead of silently
logging to the terminal; return the log shutdown error from Finish
- build.sh: -X flags used the wrong module path, so the version, build
time and commit were never stamped