fix: check stderr for lib_std.sh color detection

[codeforester]

Summary

lib/bash/std/lib_std.sh initializes colors by checking whether stdout is a terminal, but the logging helpers write to stderr. When stdout is redirected while stderr is still attached to a terminal, log color is disabled even though the log stream can render it.

Action

• Update __init_colors__ to check file descriptor 2 instead of file descriptor 1.
• Add focused coverage for the redirected-stdout/stderr-terminal case where practical.
• Preserve existing opt-out behavior when color is disabled explicitly.

Source

From the lib_std.sh Evolution Suggestions review item: "Color detection checks the wrong file descriptor."