Move from .github/copilot-instructions.md to AGENTS.md

Author: jamescmartinez

.github/copilot-instructions.md

@@ -0,0 +1,5 @@
+- Check changes against ARCHITECTURE.md & README.md and flag any inconsistencies
+- Ensure new code follows the existing coding standards and style used elsewhere
+- Verify that all new code has appropriate tests
+- Always run the full CI checks (`npm run ci`) covering formatter, linter,
+  tests, build, and typecheck; report results