Expand and clarify MgGrid system documentation
Major overhaul of MgGrid-related documentation:
- README.md: Reference full technical docs, update key files list, add new components.
- ARCHITECTURE.md: Add MgGridToolbarTemplate, MgGridSignalRDataSource; clarify component roles.
- GLOSSARY.md: Add comprehensive MgGrid System section with cross-references.
- MGGRID.md: Rewrite overview, hierarchy, CRUD, event wiring, lifecycle, layout, InfoPanel, toolbar, and data column sections for accuracy and completeness.
- copilot-instructions.md: Refine .md sync convention, add documentation layering rule.
- CONVENTIONS.md: Remove redundant code reuse section.
Brings docs in sync with codebase and improves clarity for developers.
Loretta
453e21a844