add-javadoc

Add comprehensive JavaDoc documentation to all public classes and methods. ## Class-Level Documentation For each public class: - Add class-level JavaDoc describing the purpose and responsibility of the class - Include `@author` tag if appropriate ## Method-Level Documentation For each public method: - Add method-level JavaDoc describing what the method does - Include `@param` tags for all parameters with clear descriptions - Include `@return` tag describing the return value - Include `@throws` tags for any checked exceptions ## Style Guidelines - First sentence should be a concise summary - Use HTML tags sparingly (prefer plain text) - Document preconditions and postconditions when relevant - Include code examples with `{@code ...}` for complex methods See [references/example.md](references/example.md) for before/after examples.