Add a root-gated "Halt a running server" operation to the break-glass
console. The operator picks a server from the live fleet and the console
flips that MinecraftServer CRD's spec.desiredState to Stopped via a
spec-only merge patch, disjoint from the operator's status writes, so it
cannot race or clobber reconciliation. It is the panel-independent
emergency stop for when the box still has root plus a kubeconfig.
System servers (login/lobby) are allowed but flagged: a system tag in the
picker and an explicit WARNING in the post-exit summary, since halting
login takes the shared auth front door down with no fallback. Audit is
best-effort so a halt still works with the audit sink down. Already-stopped
is a distinct no-op. The core (halt.go) is unit-tested against a real
controller-runtime fake client that applies the patch.
