refactor(wfdb): modernize reader/writer API and improve robustness

• Rename WFDB reader/writer members using m_/p_ naming convention
• Rename channel data types and writer frame structures for consistency
• Update all examples and test applications to use the new API
• Replace integer open-state flags with bool
• Strengthen parameter validation across reader and writer APIs
• Improve error handling for record, annotation, and binary parsing functions
• Enhance block read validation and EOF handling
• Refactor annotation handling with clearer state management
• Improve memory management and cleanup during open/close operations
• Free dynamically allocated signal metadata during writer shutdown
• Reset internal pointers after cleanup to prevent stale references
• Improve formatting, naming consistency, and inline documentation
• Update writer frame handling to use typed channel data members
• Rename public API parameters for improved readability and maintainability
• Add remaining unit test cases and update existing tests for API changes
• added agents.md file