A node's own readiness and its multi-node readiness are kept apart

doctor sums findings up as two readinesses - the node's, which decides
whether it joins, and multi-node, its fabrics for replicas spanning nodes -
prints fabric findings in a section of their own, and gives both in --json.
node add says the multi-node one. NodeView.multi_node says whether a node's
declared fabrics are up, naming adapters that are down, and ctl nodes shows
it beside the fabric.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/admin-api.openapi.json

@@ -5038,6 +5038,10 @@
             },
             "description": "EngineVersions are the installed engines with their versions: llamacpp → b10991. ComputeCapabilities are its GPUs' CUDA compute capabilities, 7.0 for a V100, so an engine build's support can be read against them."
           },
+          "multi_node": {
+            "type": "string",
+            "description": "MultiNode is whether it can take part in replicas spanning nodes: \"ready\", \"down: mlx5_1\" naming the declared adapters whose ports are not active, or empty for a node on no fabric. Its own replicas run either way."
+          },
           "compute_capabilities": {
             "type": "array",
             "items": {