Evaluate and add Apple container as supported runtime in CLI

[nezhar]

Summary:
Evaluate the feasibility of adding Apple's container technology as a supported runtime in the vibepod-cli tool. If feasible, implement and document the integration.

Tasks:

• Research requirements and APIs for integrating Apple container as a runtime.
• Assess compatibility and potential benefits/limitations versus existing supported runtimes.
• If suitable, implement initial support for Apple container:
  • Update configuration to allow selection of Apple container as a runtime.
  • Ensure proper detection and error handling when running on unsupported systems.
  • Cover implementation with relevant unit/integration tests.
• Update documentation to include usage, prerequisites, and known limitations.
• (Optional) Solicit feedback from users with Apple environments.

Acceptance Criteria:

• Apple container can be selected as a runtime (if feasible) in the CLI.
• Documentation is updated.
• Validation and tests added.

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If integrating Apple container is not feasible or practical, document the investigation and reasoning in this issue.