feat(k8s): deploy 3-node k3s HA control plane over Tailscale

Bootstrap a regular (non-ITAR) k3s cluster on cnode1/2/3 with embedded
etcd. All cluster communication — node registration, API server, etcd
peering, flannel VXLAN — runs exclusively over Tailscale IPs. Zero LAN
addresses appear in node status or TLS certificates.

Scripts (k8s/):
- env.sh: shared config (Tailscale IPs, SSH opts, k3s version)
- wipe.sh: remove existing k3s from all cnodes
- install-cp.sh: full bootstrap (cnode1 --cluster-init, then cnode2/3 join)
- join-servers.sh: re-join cnode2/3 only (fixes broken join state)
- post-setup.sh: apply NoSchedule taints, fetch kubeconfig, verify
- verify.sh: 13-point health check (nodes, Tailscale IPs, taints, etcd,
  CoreDNS, API server, workload isolation)
- probe-nodes.sh: SSH + Tailscale reachability check

All 3 cnodes are tainted control-plane:NoSchedule so no user workloads
can schedule on the control plane. 13/13 health checks pass.

Docs updated: k8s README TL;DR reflects k3s (not Talos) as the deployed
choice, with Talos preserved for the future ITAR cluster.

💘 Generated with Crush

Assisted-by: Crush:glm-5.2

k8s/wipe.sh

@@ -0,0 +1,52 @@
+#!/usr/bin/bash
+#
+# k8s/wipe.sh — remove existing k3s from all cnodes
+#
+# The current install on cnode1/2 uses LAN IP (192.168.3.x). We need to
+# rebuild with Tailscale IPs. This cluster has only system pods (16h old,
+# no user workloads), so a clean wipe is safe.
+#
+set -uo pipefail
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+# shellcheck source=./env.sh
+source "$SCRIPT_DIR/env.sh"
+
+echo "============================================"
+echo "  Wiping existing k3s from all cnodes"
+echo "============================================"
+
+for ip in "${ALL_CNODES[@]}"; do
+  echo ""
+  echo "--- $ip ---"
+  cn "$ip" '
+    # Stop services first
+    systemctl stop k3s 2>/dev/null || true
+    systemctl stop k3s-agent 2>/dev/null || true
+
+    # Server uninstall (also removes agents)
+    if [ -x /usr/local/bin/k3s-uninstall.sh ]; then
+      /usr/local/bin/k3s-uninstall.sh
+    elif [ -x /usr/local/bin/k3s-agent-uninstall.sh ]; then
+      /usr/local/bin/k3s-agent-uninstall.sh
+    else
+      echo "no k3s installed on this node"
+    fi
+
+    # Clean up residual state
+    rm -rf /etc/rancher/k3s /var/lib/rancher/k3s /var/lib/kubelet /var/lib/cni
+    rm -f /etc/systemd/system/k3s.service /etc/systemd/system/k3s-agent.service
+    systemctl daemon-reload
+
+    # Clean network interfaces left by k3s/flannel
+    ip link delete cni0 2>/dev/null || true
+    ip link delete flannel.1 2>/dev/null || true
+    ip link delete kube-ipvs0 2>/dev/null || true
+
+    echo "WIPE DONE"
+  '
+done
+
+echo ""
+echo "============================================"
+echo "  Wipe complete. Ready for bootstrap."
+echo "============================================"