Feature request: Add 'disableProjectCommands' setting

Use case

I have personal slash commands in ~/.claude/commands/ that I want to use across all projects. However, some projects have their own .claude/commands/ folder with commands I don't need (or duplicates).

Currently, both sources are loaded and are creating bloat, and there's no way to disable project commands locally without modifying the repo.

Requested behavior

Add a disableProjectCommands: true option in .claude/settings.local.json (gitignored).

When enabled:

• Ignore .claude/commands/ from the project
• Only load ~/.claude/commands/

Why this matters

This would be especially useful for:

• Users with centralized personal commands (e.g., via symlinks to a dotfiles repo)
• Teams where individual developers have different tooling preferences without affecting the shared repo

Alternative considered

• Deleting/gitignoring .claude/commands locally — but this requires manual intervention in every worktree and can cause git issues
• Renaming user commands to avoid conflicts — but this defeats the purpose of having a unified personal toolset