- Add mql4-syntax-critical.instructions.md: Complete syntax rules for MQL4
- Add mql4-experts.instructions.md: Expert Advisor development guidelines
- Add mql4-indicators.instructions.md: Custom indicator development guidelines
- Add mql4-scripts.instructions.md: Script development guidelines
- Update copilot-instructions.md: Add language-specific instruction routing
- Include MQL4 vs MQL5 comparison table and workflow guidance
- Based on real-world experience from MultiTimeframeZone EA development
