server: build status payload from expanded machines

StatusPayload was re-resolving grouped machines from the raw
cfg.Groups configs, so glob hosts like a3-dott{1..12} showed up as a
single machine with an unresolved pattern host and no probe state.
Iterate the expanded cfg.Machines once, bucketing by group.

Adds TestStatusPayloadExpandsGlobs regression test.

server/config_test.go

@@ -1,6 +1,8 @@
 package main
 
 import (
+	"os"
+	"path/filepath"
 	"reflect"
 	"strings"
 	"testing"
@@ -117,3 +119,49 @@ func TestExpandHostPattern(t *testing.T) {
 		}
 	}
 }
+
+func TestStatusPayloadExpandsGlobs(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "config.yaml")
+	cfg := `
+groups:
+  - name: Aula 3
+    machines:
+      - host: a3-dott{1..3}.cs.dm.unipi.it
+machines:
+  - host: router.example.net
+`
+	if err := os.WriteFile(path, []byte(cfg), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	conf, err := LoadConfig(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	mon := NewMonitor(conf, nil)
+	p := mon.StatusPayload()
+
+	if len(p.Groups) != 1 {
+		t.Fatalf("want 1 group, got %d", len(p.Groups))
+	}
+	g := p.Groups[0]
+	want := []string{
+		"a3-dott1.cs.dm.unipi.it",
+		"a3-dott2.cs.dm.unipi.it",
+		"a3-dott3.cs.dm.unipi.it",
+	}
+	if len(g.Machines) != len(want) {
+		t.Fatalf("group machines: want %d, got %d", len(want), len(g.Machines))
+	}
+	for i, m := range g.Machines {
+		if m.Host != want[i] {
+			t.Errorf("machine %d: host %q, want %q", i, m.Host, want[i])
+		}
+	}
+	if len(p.Machines) != 1 {
+		t.Fatalf("top-level machines: want 1, got %d", len(p.Machines))
+	}
+	if p.Machines[0].Host != "router.example.net" {
+		t.Errorf("top-level host: %q", p.Machines[0].Host)
+	}
+}

server/monitor.go

@@ -658,15 +658,8 @@ func (m *Monitor) StatusPayload() statusPayload {
 		grouped[group] = append(grouped[group], ms)
 	}
 
-	for _, g := range m.cfg.Groups {
-		for _, mc := range g.Machines {
-			appendStatus(resolveMachine(mc, g.Name, m.cfg), g.Name)
-		}
-	}
 	for _, mc := range m.cfg.Machines {
-		if mc.Group == "" {
-			appendStatus(mc, "")
-		}
+		appendStatus(mc, mc.Group)
 	}
 
 	for _, name := range order {