[Idea] Replace azure-validate skill with preToolCall hook or azd built-in logic

Given that azure-validate runs a fixed sequence of steps, we should consider replacing it with hooks or azd built-in logic to more determinisitcally perform validation. This would allow us to better address the following problems:

• Agent skip validation. The hook or azd built-in logic can ensure no deployment will be attempted without passing the validation steps.
• Validation using too much tokens, causing the agent to lose attention on its previously given instructions. The script can limit the number of tokens added to the context window, making it more likely for the agent to remain focused on the prepared plan.

Start by reading the existing azure-validate skill and comparing the proposed preToolCall hook with azd built-in logic. A solution should prevent deployment until validation passes while limiting validation output added to the agent context, but the issue does not identify files or tests.