tofu: node vCPU 6 -> 8 (CPU spike headroom)

Steady-state CPU PSI 15-23% + 15-min load 5.6-8.0 on 6 cores (run queue at/over core count) left no
headroom for bursty workloads. Proxmox host has 24 cores at ~4% load, so 3x8 = 24 vCPU is 1:1 with
zero oversubscription. In-place tofu update (cores change is pending until a per-node VM stop/start);
rolled one node at a time to keep etcd quorum. Comment also corrected 16->24 GiB (stale).

Co-Authored-By: Claude Opus 4.8 <[email protected]>

infra/tofu/variables.tf

@@ -74,12 +74,16 @@ variable "node_count" {
   }
 }
 
-# --- per-node sizing (Proxmox target: 6 vCPU / 16 GiB / 64 GiB OS + 128 GiB data) --
+# --- per-node sizing (Proxmox target: 8 vCPU / 24 GiB / 64 GiB OS + 128 GiB data) --
 
 variable "vcpu" {
+  # 8 (was 6): steady-state CPU PSI was 15-23% and 15-min load 5.6-8.0 on 6 cores (run queue at/over
+  # the core count) — bursty workloads had no spike headroom. The Proxmox host has 24 physical cores
+  # at ~4% load, so 3x8 = 24 vCPU is a clean 1:1 with zero oversubscription. Roll one node at a time
+  # (etcd quorum) — `qm set` cores needs a VM stop/start, not a reboot, to take effect.
   description = "vCPUs (cores) per node. Generous — the box has plenty."
   type        = number
-  default     = 6
+  default     = 8
 }
 
 variable "memory_mib" {