release delete was CLI-only. The releases page now offers it to a repo admin
inside the existing edit disclosure, dispatching release delete <repo> <tag> --yes through runControlCode like every other web write.
Gated on CanAdmin, which is what the command itself requires — CanWrite only
gets the edit form. The CLI's --yes guards a mistyped tag; on the page the tag
comes from the release being shown, so the button is the deliberate act.
TestReleaseAndBuildWeb covers it: a reader sees no control, an admin deletes,
the release leaves release list, and the tag is offered for creation again.
Parity row updated.
Closes #165