feat(installer): activate source builds atomically

internal/installer/harness/integration_test.go

@@ -325,6 +325,9 @@ func TestSourceInstallFixtures(t *testing.T) {
 					IdentityFile:   testKeyPath(),
 					KnownHostsFile: h.KnownHostsPath(),
 				},
+				// Staging-only: service activation (work package 4) is
+				// exercised by the dedicated activation tests.
+				Activation: installer.ActivationOptions{Activate: false},
 			}
 			if repo := strings.TrimSpace(os.Getenv("RSMON_TEST_SOURCE_REPO")); repo != "" {
 				opts.Repo = repo
@@ -446,6 +449,7 @@ func TestSourceInstallDirtyCheckoutPreservesStaging(t *testing.T) {
 			IdentityFile:   testKeyPath(),
 			KnownHostsFile: h.KnownHostsPath(),
 		},
+		Activation: installer.ActivationOptions{Activate: false},
 	}
 	if repo := strings.TrimSpace(os.Getenv("RSMON_TEST_SOURCE_REPO")); repo != "" {
 		opts.Repo = repo