bees: write --show-config ROOT_PATH diagnostics straight to stderr

bees: write --show-config ROOT_PATH diagnostics straight to stderr

The reason text is one string with embedded newlines, wrapped at 80
columns, written to cerr together with the specific failure in a single
insertion so the lines cannot interleave with other output.  Going to
stderr directly means the message is visible regardless of the log
configuration, which is the right behaviour for a command-line usage
error in bees_main.

Assisted-by: Claude-Code:claude-fable-5-1