fix(redirect): `2>/dev/null` does not suppress stderr from builtins

[chaliy]

Summary

Redirecting stderr to /dev/null via 2>/dev/null does not suppress error output from builtin commands. The stderr content still appears on the terminal.

Reproduction

echo "error msg" 2>/dev/null
# Expected: "error msg" on stdout only, stderr suppressed
# Actual: works for echo (stdout), but...

ls /nonexistent 2>/dev/null
# Expected: no output
# Actual: error message still visible

Also affects &> combined redirect:

ls /nonexistent &> /dev/null
# Expected: no output at all
# Actual: error still shows (exit code 2 is correct)

Context

Discovered while running bashblog via bashkit CLI. Bashblog uses &> /dev/null and 2>/dev/null extensively to suppress expected errors:

• ls ./*.html &> /dev/null
• cp .backup.tar.gz .yesterday.tar.gz &> /dev/null
• rm ./"$prefix_tags"*.html &> /dev/null

Expected behavior

2>/dev/null should discard all stderr output. &>/dev/null should discard both stdout and stderr.