feat: add structured error tracking with stack trace parsing

[kashishhora]

Summary

Added

• New captureException() function that parses V8 stack traces into structured data
• Stack frame parsing with file paths, line numbers, function names, and in_app detection
• Error cause chain unwrapping (Error.cause support)
• Path normalization for consistent error grouping across deployments
• New ErrorData, StackFrame, and CauseData types for structured error tracking
• Comprehensive test suite for exception capture and stack trace parsing

Modified

• Replaced getMCPCompatibleErrorMessage() with captureException() across all tracing modules
• Updated error handling in tracing.ts, tracingV2.ts, and internal.ts to use structured error data
• Simplified error message extraction in Sentry exporter
• Updated Event.error type from object to ErrorData for type safety

Test Plan

• Run the test suite (npm test) to verify all exception capture tests pass
• Test error tracking with various error types (Error, TypeError, ReferenceError, custom errors)
• Verify stack traces are properly parsed and normalized across different environments
• Confirm error cause chains are correctly unwrapped
• Check that in_app detection properly identifies user code vs library code