Bash tool uses login shell (-l) causing unwanted output

Issue

Every bash command is executed as a login shell, sourcing ~/.bash_profile / ~/.profile on each invocation. This pollutes command output with login script messages and adds unnecessary overhead.

Steps to Reproduce

1. Add any output statement to ~/.bash_profile (e.g., echo "Login shell initialized")
2. Execute any Bash tool command through Claude Code
3. Observe the extra output from the login script

Verification

$ shopt login_shell
login_shell     on

Expected

Commands should run in non-login shells. The -l flag should not be used unless specifically needed.

Impact

• Extraneous output in command results
• Performance overhead from repeatedly sourcing login scripts
• Unexpected environment modifications