Give the uplink seat its verbs, optional until its holders serve them (hq ADR 0241)

What a machine resolves through and over which links had no tool: the
resolver file and its writer, and each link with its routes and resolvers,
are now verbs of node-uplink, the same whatever manages the network. Marked
optional (Verb.Optional), so today's holders still hold the seat until both
serve them; read back from the store's row they stay optional.

internal/catalogue/seats.go

@@ -281,7 +281,12 @@ var defaultSeats = append([]Seat{
 	// channel a fix could arrive on. A seat
 	// rather than a condition in the resolver's module, so a machine running two managers is
 	// refused at assignment instead of found by the resolver being rewritten (novox/hq ADR 0117).
-	{Name: "node-uplink", Scope: ScopeNode, Decision: "novox/hq ADR 0117"},
+	//
+	// Its verbs say what the machine resolves through and over which links (novox/hq ADR 0241): the
+	// resolver file as it is and who wrote it, and every link with its addresses, routes and the resolvers
+	// the manager knows for it — the same for every holder, so a question about a machine's names is asked
+	// the same way whatever manages its network. Optional until both holders serve them.
+	{Name: "node-uplink", Scope: ScopeNode, Decision: "novox/hq ADR 0117", Serves: uplinkVerbs()},
 },
 	// The graphical session's roles (novox/hq ADR 0208), last because they are a workstation's.
 	graphicalSessionSeats()...)
@@ -635,6 +640,22 @@ func serviceManagerVerbs() []Verb {
 	}
 }
 
+// uplinkVerbs is the contract every holder of node-uplink serves (novox/hq ADR 0241): read-only answers
+// about what the machine resolves through and over which links, whatever program manages its network.
+func uplinkVerbs() []Verb {
+	return []Verb{
+		{Name: "resolvers", Description: "The machine's resolver file as it is now: the resolvers, search " +
+			"domains and options it lists, whether it is the file the mesh declares, and when it is not, who " +
+			"wrote it as far as the machine shows — its header, a backup a VPN client left beside it, a link " +
+			"in its place, a known writer running.",
+			Input: schema(nil, nil), Optional: true},
+		{Name: "links", Description: "Every network link on the machine: its state, its addresses, whether " +
+			"the default route leaves through it, and the resolvers and search domains the network manager " +
+			"knows for it — a VPN's tunnel included.",
+			Input: schema(nil, nil), Optional: true},
+	}
+}
+
 // loginShellVerbs is the contract every holder of node-login-shell serves (novox/hq ADR 0176, ADR
 // 0204): one command, run the way the operator's own terminal would run it, bounded below the
 // runtime's thirty-second call limit so a hung command answers rather than times the caller out.