Raise a machine's network from what its engine says, once (hq ADR 0241)

A VPN client rewrote the laptop's resolver file and nothing said so. The
engine now states its machine's networking; the controller keeps it with
the machine's health (migration 0077) and raises the rewrite as its own
finding naming the writer, the machine's own faults as machine.<m>.network,
and what several machines cannot reach once, there. The gate waits on a
rewrite it did not make rather than putting back a good build.

internal/link/protocol.go

@@ -428,6 +428,45 @@ type Health struct {
 	// At is when the engine looked, on the machine's clock: the order of its statements.
 	At        time.Time        `json:"at"`
 	Resources []ResourceHealth `json:"resources"`
+	// Network is the machine's own networking, judged by its engine (novox/hq ADR 0241); nil from an engine
+	// older than that judging, which is "not known", never healthy.
+	Network *NetworkHealth `json:"network,omitempty"`
+}
+
+// NetworkHealth is a machine's networking in one statement (ADR 0241): the worst of its parts, since
+// when, and each part. The node-engine's own (mesh-host internal/link NetworkHealth).
+type NetworkHealth struct {
+	State string        `json:"state"`
+	Since time.Time     `json:"since"`
+	Parts []NetworkPart `json:"parts"`
+}
+
+// The parts of a machine's networking its engine judges (ADR 0241).
+const (
+	PartResolvConf = "resolv-conf"
+	PartNames      = "names"
+	PartTunnel     = "tunnel"
+	PartBus        = "bus"
+	PartRoute      = "route"
+	// TowardHub is what a part failing toward the hub names in Toward.
+	TowardHub = "hub"
+)
+
+// NetworkPart is one part, as the engine judged it on its second look.
+type NetworkPart struct {
+	Part  string `json:"part"`
+	State string `json:"state"`
+	// Reason is in words with no address, path or domain; Said is the detail, kept as evidence.
+	Reason string `json:"reason,omitempty"`
+	Said   string `json:"said,omitempty"`
+	// Writer is the program that rewrote the resolver file, when the engine could name it; Owner the
+	// module whose file it is.
+	Writer string `json:"writer,omitempty"`
+	Owner  string `json:"owner,omitempty"`
+	// Toward is what a failure points at: "hub", or each resolver's address that failed.
+	Toward []string  `json:"toward,omitempty"`
+	Since  time.Time `json:"since"`
+	Streak int       `json:"streak,omitempty"`
 }
 
 // The states a resource is said in (ADR 0240 §4).