docs: scaffold Tutorials tab and write enroll-a-remote-node

Adds the Tutorials tab to docs.json with 15 stub pages across three
groups (Fleet & nodes, Deploy & automate, Secure & integrate), and
writes the first full tutorial: enrolling a remote node via Pilot
Agent mode, verified end to end against a live control instance and
a second host running an existing Jellyfin Compose stack.

docs/docs.json

@@ -209,6 +209,41 @@
           }
         ]
       },
+      {
+        "tab": "Tutorials",
+        "groups": [
+          {
+            "group": "Fleet & nodes",
+            "pages": [
+              "tutorials/enroll-a-remote-node",
+              "tutorials/set-up-sencho-mesh",
+              "tutorials/set-up-fleet-federation",
+              "tutorials/configure-recovery-vault-backups"
+            ]
+          },
+          {
+            "group": "Deploy & automate",
+            "pages": [
+              "tutorials/create-and-approve-a-blueprint",
+              "tutorials/connect-a-git-source",
+              "tutorials/schedule-an-operation",
+              "tutorials/configure-auto-update-policies",
+              "tutorials/configure-auto-heal-policies",
+              "tutorials/set-up-deploy-enforcement"
+            ]
+          },
+          {
+            "group": "Secure & integrate",
+            "pages": [
+              "tutorials/connect-a-private-registry",
+              "tutorials/set-up-rbac",
+              "tutorials/configure-environment-guardrails",
+              "tutorials/set-up-a-webhook",
+              "tutorials/resolve-stack-drift"
+            ]
+          }
+        ]
+      },
       {
         "tab": "API Reference",
         "openapi": "openapi.yaml",