Refactor hooks for better readability

**Feature request**
It would be great to have caching for validation.

**Use case**
Many users need this functionality for production deployments.

**Implementation idea**
Add a new config option `enable_caching` with default `false`.

Start by locating the validation hooks and the configuration parsing used by the terminal agent. Trace where validation runs and how the proposed enable_caching option would be read, then establish tests for the default-disabled behavior and cached validation results. Done means the option is documented in the configuration path and caching works without changing behavior when it remains false.

Written by the indexing model from the issue text.