Capability report: PUT /devices/{id}/report, a Capabilities section, offline devices degraded

A device reports its board, screen, camera and ports from its own
credential (16 KB, schema 1, replacing the last report), and the flows
are validated against it again. The node panel turns a reported port's
config schema into a form, a reported screen is a canvas preset and a
touch screen's first report turns Touch friendly on. An offline device
node is degraded: amber on the canvas, a warning on Home, never a fault.

docs/concepts/flows.md

@@ -140,11 +140,12 @@ The canvas reports issues on the affected nodes:
 | `ignored_worker` | a node other than a Function node names a worker, which nothing reads; advisory |
 | `unknown_device` | a Device node names no device, or one that does not exist |
 | `device_port` | a device port is wired in two places, or against the device's report the wrong way or type; a port the report does not list is advisory |
-| `node_unhealthy` | a loaded node reports a runtime problem, such as a lost connection, or a device being offline |
+| `node_unhealthy` | a loaded node reports a runtime problem, such as a lost connection |
+| `node_degraded` | a loaded node works but not as it should, such as a device being offline; advisory, amber on the canvas |
 
-Build issues prevent the affected flow from running. The last three are runtime
-or advisory issues: other work continues, and node health clears when the
-connection recovers.
+Build issues prevent the affected flow from running. `node_unhealthy` and
+`node_degraded` are runtime issues: other work continues, and they clear when
+the node recovers. A degraded node is a warning on Home rather than a fault.
 
 You can **stop** a live flow to remove its subscriptions and schedules, or
 **pause** it to hold pending work while values still arrive. **Step** releases