feat(destroy): default to robust destroy for all gcluster destroy operations

[Neelabh94]

This PR makes robust as the default for destroy.

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[gemini-code-assist]

Summary of Changes

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This pull request modifies the default behavior of the destroy command by enabling the robust destruction process automatically. This change ensures that firewall rule cleanup is performed by default, while still allowing users to opt-out by explicitly passing the flag.

Highlights

• Default behavior change: Updated the 'robust' flag in the destroy command to be enabled by default.
• Documentation update: Updated the command-line documentation to reflect that the robust destroy process is now the default behavior.

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[gemini-code-assist]

Code Review

This pull request changes the default value of the --robust flag in the destroy command from false to true and updates the documentation accordingly. However, feedback highlights that setting this to true by default introduces a critical regression: if the firewall cleanup fails, the command aborts early and skips the actual terraform destroy for subsequent groups. The reviewer recommends keeping the default as false or refactoring the cleanup to be non-fatal.

[gemini-code-assist]

Changing the default of --robust to true introduces a critical regression in the destroy command.

The Issue

When robustDestroy is true (which is now the default), destroyGroup attempts to clean up firewall rules if a network module is present. If this cleanup fails (e.g., due to missing ADC or permissions), it immediately aborts the loop, skipping the actual terraform destroy for this and subsequent groups.

Recommendation

In accordance with our state cleanup guidelines, we should use a best-effort approach for cleanup operations. Instead of failing fast and aborting the entire destroy sequence, the firewall cleanup failures should be logged as errors/warnings and the process should continue. This ensures maximum cleanup of remaining infrastructure and avoids blocking subsequent teardown retries. Alternatively, keep the default as false until the cleanup error handling is refactored to be non-fatal.

Suggested change

	destroyCmd.Flags().BoolVar(&robustDestroy, "robust", true, "Perform a robust destroy, including firewall rule cleanup.")
	destroyCmd.Flags().BoolVar(&robustDestroy, "robust", false, "Perform a robust destroy, including firewall rule cleanup.")

References

1. When performing state cleanup (such as removing unreachable resources from Terraform state), use a best-effort approach by logging errors and continuing rather than failing fast or returning a combined error. This ensures maximum cleanup of remaining infrastructure and avoids blocking subsequent teardown retries.