feature: gh aw verify command

[brunoborges]

To simply verify if an agentic workflow is producing valid action workflow, users are required to run the following command:

$ gh aw compile --validate --no-emit daily-issues-report.md

It would be easier to have a verify command that is a short hand for the --validate and --no-emit operations:

$ gh aw verify daily-issues-report.md

Note: the command may as well be called validate, but IMO that would be the same as compile --validate where to me, verify is also about --no-emit. And having both validate/verify as additional commands, would be confusing to most users who can't fully understand the semantics of the word validate versus verify.

[pelikhan]

Add a new validate command that runs the compiler in no-emit mode with the validate flag, and with Zizmor, actionlint, and poutine modes enabled. This command ensures that the action is compliant with all supported linters.