Add tests for cli entrypoint

[kalenkevich]

Summary

Refactors the CLI entrypoint to improve testability and adds comprehensive unit tests for all CLI commands.

Changes

• Refactor CLI Entrypoint: Modified dev/src/cli/cli.ts to export a createProgram function instead of executing immediately. This allows the CLI configuration to be tested in isolation.
• New Entrypoint File: Created dev/src/cli_entrypoint.ts as the new executable entry point that invokes createProgram.
• Test Coverage: Added dev/test/cli/cli_test.ts achieving high coverage for:
  • version command
  • web command (AdkWebServer options)
  • api_server command
  • create command (Agent creation options)
  • run command (Agent execution options)
  • deploy cloud_run command