fix: normalize npm bin paths

[papperrollinggery]

Summary

• Normalize npm bin paths to the format npm publish auto-corrects to.
• Add public audit assertions for CLI bin mappings.

Verification

• npm run build
• npm run lint
• npm test
• npm run audit:public
• npm publish --dry-run --tag beta --access public
• tarball install smoke with lb, lazybrain, and lazybrain-mcp
• npx gitnexus detect_changes --repo lazy-brain