New Artifact tool "version" action

The artifact tool gains a version action that runs a dedicated version-resolution flow with retry progress reporting and updates the artifact's read-version state afterward; it's rejected if the live-doc module isn't available in the build, and re-validates the approved action and URL still match before running, guarding against a changed target between approval and execution. getToolUseSummary and the auto-classifier describe version as versioning an artifact with nothing uploaded.

Alongside version, a new open action lets Claude show an existing artifact read-only, distinct from list/publish, and is treated as read-only by the classification logic. New get_handlers, call_handler, and run_script actions add server-callable handler support, gated by boolean flags in the tool constructor and an ACTION description clause added to the schema when handlers are enabled; get_handlers is classified read-only, while call_handler/run_script are treated as writes unless a handlers-action-write check says otherwise. These gates are logged in the schema-build telemetry line and folded into the action enum.