cpupick: Keep single readers off tun.avoid_cpus without cpupick, warn and ignore bad lists

examples/config.yml

@@ -296,12 +296,12 @@ tun:
   #  - 4
 
   # Linux only. avoid_cpus lists CPU IDs the tun readers are never pinned to, exactly as listed (SMT siblings are not
-  # added for you). The default pin selection skips them, even with a single routine, and a cpu_affinity entry naming
-  # one is rejected like any other invalid entry. Other threads are not restricted, and the setting does nothing with
-  # pin_threads: false. Invalid IDs, or IDs covering every allowed CPU, fail startup. Not reloadable. To keep Nebula
-  # off the underlay NIC's receive IRQ CPUs, find them in /proc/interrupts and /proc/irq/<IRQ>/effective_affinity_list,
-  # add their SMT siblings from /sys/devices/system/cpu/cpu<N>/topology/thread_siblings_list if you want those kept
-  # clear too, and revisit the list when IRQ placement changes.
+  # added for you). The default pin selection skips them, and a cpu_affinity entry naming one is rejected like any
+  # other invalid entry. Other threads are not restricted, and the setting does nothing with pin_threads: false. An
+  # invalid list, or one covering every allowed CPU, is ignored with a warning. Not reloadable. To keep Nebula off the
+  # underlay NIC's receive IRQ CPUs, find them in /proc/interrupts and /proc/irq/<IRQ>/effective_affinity_list, add
+  # their SMT siblings from /sys/devices/system/cpu/cpu<N>/topology/thread_siblings_list if you want those kept clear
+  # too, and revisit the list when IRQ placement changes.
   #avoid_cpus: []
 
   # Route based MTU overrides, you have known vpn ip paths that can support larger MTUs you can increase/decrease them here