Add and delete Actor versions over MCP (create-actor-version, delete-actor-version) #1475

The version tools of the Actor source tools spec (#1452). The API's version update cannot create a version, so without them an agent cannot add a version next to the one in use.

create-actor-version adds a version to an existing Actor, from files or as a copy of another version stored as files. A copy takes the other version's files, its non-secret env vars, and applyEnvVarsToBuild, never its build tag, so builds of a working copy never move a tag such as latest.

delete-actor-version deletes one version. The platform refuses to delete the last one.

The platform still decides a taken version number, the limit of 10 versions per Actor, the limit on the combined size of all versions, the last-version rule, and permissions. A permission error reaches the agent as it does for any other tool. The other refusals come back with the platform's message and error type, without the hint that the token may lack access.

Acceptance

• create-actor-version and delete-actor-version in the source category (feat: Add create-actor-version and delete-actor-version tools #1454)