docs(fleet): add operator configuration guide

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/fleet/how-to/configure-ultron-validator.md

@@ -0,0 +1,21 @@
+# Configure a Validator Instance
+
+A validator instance is a configurable local roster member with canonical `class: validator` and matching `tool_policy: validator`. “Ultron” may be used as a display alias, but it is not a required identity, class alias, product name, or source of authority.
+
+Use the [validated generic roster](../examples/roster-v2.yaml) as the safe shape. Choose a unique stable name and explicit supported runtime/provider/model/reasoning values. Start stopped:
+
+```yaml
+name: validator-example
+alias: Validator Example
+class: validator
+tool_policy: validator
+lifecycle:
+  enabled: true
+  desired_state: stopped
+```
+
+Plan the full payload with the current generation and create without `--persisted-start`. Creation writes desired state and projections only; it does not launch a validator.
+
+`validator` may issue independent validation evidence or a certificate. It has no approve-to-land or merge authority. `merge-gate` remains the sole protected merge authority, and changing the validator's name, alias, persona prose, runtime, provider, model, or tool-policy text cannot elevate it.
+
+Certificate consumption and final release evidence remain FCM-M5-002 gates. This page does not create a certificate or authorize merge. See [safe CRUD](create-update-delete-agent.md) and [role authority](../concepts/role-authority-and-leases.md).