add guidance for Copilot on code style and testing practices

docs/README.codestyle.md

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+# README.codestyle.md
+
+This file provides guidance to Copilot about code style and conventions in this repository.
+
+## Formatting and indentation of files
+
+DO NOT fix code indentation or formatting as part of work done by Copilot.  
+Other tools will handle that.
+
+## JSDoc comments
+
+- Describe what the function does
+- List all parameters, including (if possible) what properties object parameters have
+- List possible return values, including Promises and data types. Insert empty line between parameters and return value descriptions.

docs/README.testing.md

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+# README.testing.md
+
+This file provides guidance to Copilot about testing practices in this repository.
+
+## Unit tests
+
+- Verify tests work after creation new test files.
+- Do not fix linting or formatting issues in tests. These will be handled later using other tools.
+- Run tests using "npm run test".