Fix(cli): validate agent folder name for dashes in agent_engine deploy

[Ahmed-Ali-313]

Description

Fixes #2902

When deploying an agent using adk deploy agent_engine where the agent folder name contains dashes (e.g., my-agent-folder), Vertex AI Agent Engine fails at deployment runtime with a Python syntax error (invalid syntax (agent_engine_app.py)) because module names in Python cannot contain dashes.

Changes

• Added _validate_agent_folder_name in cli_deploy.py to validate that the agent directory name is a valid Python identifier before deployment begins.
• Provided a clear and actionable error message suggesting an underscore-based alternative (e.g., my_agent_folder).
• Added unit tests in test_cli_deploy.py verifying validation behavior for valid and invalid names.

Test Plan

• Ran pytest suite: pytest tests/unittests/cli/utils/test_cli_deploy.py (54 passed).

[Ahmed-Ali-313]

Hi @wyf7107,

I have submitted this PR to resolve #2902 by adding pre-deployment validation for agent folder names in cli_deploy.py.

It validates that the agent directory name is a valid Python identifier, preventing runtime syntax errors on Agent Engine caused by dashes, and provides a clear, actionable error message suggesting an underscore-based alternative.

All unit tests have been added and verified. Whenever you have a moment, please review the changes. Thank you