Under the hood
Artifact tool's input-validation checks reordered and error codes renamed
**What
The artifact_bash tool's input-validation logic now runs a combined check earlier than before, reuses existing helper functions, and replaces some error codes for local-only and eval-stub validation checks with named constants instead of raw values.
**Why
This is an internal code-quality change to how validation errors are structured; it doesn't change what triggers a validation error, just how it's represented internally.