Hook Context Env

hook-context-env experiment exposes additional TG_CTX_* env vars to hooks

Enable the new hook-context-env experiment to surface three additional environment variables to every before_hook, after_hook, and error_hook:

• TG_CTX_HOOK_TYPE — before_hook, after_hook, or error_hook, identifying which lifecycle phase invoked the hook.
• TG_CTX_SOURCE — the resolved terraform source URL (CLI --source override, else evaluated terraform.source with source-map applied, else .).
• TG_CTX_TERRAGRUNT_DIR — the directory of the current Terragrunt config.

terragrunt run --all --experiment hook-context-env -- apply

These variables make it easier to share a single hook script across lifecycle phases and to access the unit's source and config directory without threading them through hook arguments.