feat: implement automatic bidirectional environment variable synchronization

[tinovyatkin]

Summary

This PR implements automatic bidirectional environment variable synchronization between Python JSII runtime and Node.js kernel processes, as specified in the design document.

Key Features

• Zero configuration required - works automatically when both runtimes are active
• Immediate synchronization via synchronous IPC communication
• Bidirectional sync - changes in either Python or Node.js are reflected in both
• Thread-safe operations with proper locking for concurrent access
• Comprehensive test coverage with 79 passing tests

Implementation Components

Node.js/TypeScript Side

• EnvironmentMonitor class: Proxy-based monitoring of process.env changes
• Enhanced Kernel API: Added env.notifyChange method for external synchronization
• Comprehensive tests: Full coverage of EnvironmentMonitor, Kernel integration, and API types

Python Side

• PythonEnvironmentMonitor: Wrapper for os.environ with automatic change detection
• Enhanced ProcessProvider: Bidirectional sync logic between runtimes
• Thread-safe implementation: Proper locking mechanisms for concurrent access

Test Infrastructure

• TypeScript tests: 3 test suites with 79 passing tests
• Python tests: Comprehensive testing of Python-side functionality
• Integration utilities: Test helpers in jsii-calc for end-to-end validation

Technical Details

The implementation uses:

• Proxy objects to intercept environment variable access
• Synchronous IPC for immediate change propagation
• Callback-based architecture for cross-runtime communication
• Proper type definitions for TypeScript and Python
• Extensive error handling and edge case coverage

Files Changed

• 12 files modified with 2,078 insertions and 3 deletions
• 7 new files created for core functionality and comprehensive testing
• 5 existing files enhanced to support environment synchronization

Test plan

• [x] All existing tests continue to pass
• [x] New TypeScript tests pass (79/79 tests passing)
• [x] New Python tests pass with comprehensive coverage
• [x] Manual testing of bidirectional synchronization
• [x] Edge case testing (null/undefined values, concurrent access, etc.)
• [x] Integration testing with jsii-calc utilities

🤖 Generated with Claude Code

[rix0rrr]

This PR is missing a description of what problem it is solving, and why and how it solves it.