includeCoAuthoredBy: false setting not enforced when using Bash tool for git commits

Bug Report

Expected Behavior

When includeCoAuthoredBy is set to false in ~/.config/claude-code/settings.json, Claude Code should not add co-authorship branding to any git commits, regardless of how the commit is made.

Actual Behavior

The setting only prevents branding in some cases. When Claude uses the Bash tool to directly craft commit messages (e.g., git commit -m "..."), it can still include the branding lines:

• 🤖 Generated with [Claude Code](https://claude.com/claude-code)
• Co-Authored-By: Claude <noreply@anthropic.com>

Configuration

Settings file contains:

{
  "includeCoAuthoredBy": false
}

Steps to Reproduce

1. Set includeCoAuthoredBy: false in ~/.config/claude-code/settings.json
2. Ask Claude to create a git commit using the Bash tool
3. Observe that branding is still added to the commit message despite the setting

Suggested Fix

The setting enforcement should happen at a lower level - either:

• Intercept git commit commands and strip branding before execution
• Hook into git commit-msg to sanitize messages
• Provide stronger guidance/constraints to Claude about respecting this setting

The current behavior suggests the setting may only affect certain code paths but not when Claude manually crafts commit messages through the Bash tool.

Environment

• Claude Code CLI
• OS: Linux (NixOS)
• Setting verified to be false in settings.json