Add comprehensive tests and documentation for native/container support

Added unit tests, module documentation, and detailed feature guides
for the new native process and container orchestration capabilities.

New unit tests:
- NativeProcessLauncherTest (7 tests)
  - Configuration validation
  - Error handling for missing executables
  - Process lifecycle management
  - Graceful handling of dead/null processes

- ContainerLauncherTest (11 tests)
  - Runtime detection (Docker, Podman, LXC)
  - Configuration validation
  - Image requirement validation
  - ContainerInfo data structure tests

Test summary:
- Total: 70 unit tests across 9 test classes
- All tests passing
- Focus on API contracts and configuration validation
- Integration tests require actual executables/containers

New documentation:
- NATIVE_EXECUTION.md - Complete guide to native process deployment
  - GraalVM native images
  - Compiled binaries (Rust, Go, C++)
  - Configuration properties
  - Lifecycle management
  - Use cases and comparisons
  - Future enhancements

- CONTAINER_DEPLOYMENT.md - Complete guide to container orchestration
  - Docker, Podman, LXC support
  - Image management and pulling
  - Port mappings, volumes, environment variables
  - Network configuration
  - Multiple runtime examples
  - Use cases and comparisons
  - Future enhancements

- jplatform-core/README.md - Module documentation
  - All core components documented
  - ApplicationManager (fine-grained locking)
  - Deployment modes (JVM, native, container)
  - Test coverage summary
  - Performance improvements
  - Usage examples for all deployment modes

Updated main README.md:
- Added "Native Process Execution" section
- Added "Container Orchestration" section
- Updated feature list with implementation status
- Links to new documentation

All classes have complete javadoc:
- NativeProcessLauncher - fully documented
- ContainerLauncher - fully documented with property reference
- All public methods have @param and @return tags
- Class-level documentation with usage examples

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: Flossy