feat: move all workers to zero-idle

docs/README.md

@@ -4,10 +4,10 @@
 
 ## Gitea runner labels
 
-Common labels for zero-idle runners:
+Common labels for controller-managed zero-idle runners:
 
-- `ubuntu-latest` — persistent Ubuntu 24.04 `cx23` worker
-- `nix` — persistent Nix-capable Ubuntu `cx23` worker
+- `ubuntu-latest` — zero-idle alias for `gross-x86`
+- `nix` — zero-idle Nix alias with 480-minute TTL
 - `gross-x86` — x86 fallback chain `cx53` / `cx43` / `cx33`
 - `gross-arm` — ARM fallback chain `cax41` / `cax31` / `cax21`
 - `gross-x86-perf` — x86 performance chain `cx53` / `cpx62` / `cpx52`
@@ -15,12 +15,13 @@ Common labels for zero-idle runners:
 - `gross-nix-x86` — `gross-x86` + Nix bootstrap
 - `gross-nix-arm` — `gross-arm` + Nix bootstrap
 - `gross-nix-x86-perf` — `gross-x86-perf` + Nix bootstrap
+- `gross-nix-x86-highmem` — CCX53-only Nix runner, 480-minute TTL
 - `gross-nix-mixed-econ` — `gross-mixed-econ` + Nix bootstrap
 
 Region order for fallback: `nbg1`, then `fsn1`, then `hel1`.
 
-`nix` and `ubuntu-latest` are persistent workers; only `gross-*` labels use
-zero-idle ephemeral VMs.
+The legacy Kubernetes persistent pool is disabled (`replicas: 0`) and has no
+registered labels. All listed labels are handled by the zero-idle controller.
 
 Operational details: `infra/gitea-runners/runbook.md` and
 `package/gitea-runner-controller/decide.sh`.