Point the e2e sweep at the verb that still exists

Main's af42b1be16 added sweepNativeMirrors, which calls repo mirror get <path> --json and keeps placements whose Role is "native_mirror". This branch deletes that verb and renames that role to "mirror", so after the merge the call fails, sweepList swallows the error as a skip, and leaked native mirrors are never removed. Per the sweep's own comment that is not cosmetic: the server refuses to delete a repo that still has one, so a single leak makes its repo, project and org undeletable and permanently costs one of the account's three org slots.

Nothing here could have caught it. The file is //go:build e2e and test:ci runs -tags=integration, so the gate never compiles it, and the verb reaches the CLI as a string. My own stale-verb sweeps had been grepping cmd/ and docs/ and reporting clean — true of the directories they searched, and e2e/ was never one of them.

The clone-URL host lookup stays: p.Cluster is the public host now but falls back to the slug when a cluster has none, so CloneURL remains the safer source for --cluster.