Implement direct Notarius extraction execution

internal/artifacts/paths_model_test.go

@@ -49,6 +49,33 @@ func TestSessionRunManifestPathForCampaign(t *testing.T) {
 	}
 }
 
+func TestSessionNotariusPathsForCampaign(t *testing.T) {
+	root := "/tmp/workspace"
+	campaign := "forsaken"
+	sessionID := "2026-04-19"
+	runID := "20260515T031522Z-a1b2c3d4"
+	extractDir := filepath.Join(root, "work", campaign, sessionID, "runs", runID, "extract")
+
+	tests := []struct {
+		name string
+		got  string
+		want string
+	}{
+		{name: "extract directory", got: SessionRunExtractDirForCampaign(root, campaign, sessionID, runID), want: extractDir},
+		{name: "receipt", got: SessionRunNotariusReceiptPathForCampaign(root, campaign, sessionID, runID), want: filepath.Join(extractDir, "notarius.receipt.json")},
+		{name: "stderr", got: SessionRunNotariusLogPathForCampaign(root, campaign, sessionID, runID), want: filepath.Join(extractDir, "notarius.stderr.log")},
+		{name: "output root", got: SessionRunNotariusOutputRootForCampaign(root, campaign, sessionID, runID), want: filepath.Join(extractDir, "notarius-output")},
+		{name: "durable bundle", got: SessionNotariusBundleDirForCampaign(root, campaign, sessionID, runID), want: filepath.Join(root, "work", campaign, sessionID, "artifacts", "notarius", runID)},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			if test.got != test.want {
+				t.Fatalf("path = %q, want %q", test.got, test.want)
+			}
+		})
+	}
+}
+
 func TestSessionPreviousPathsForCampaign(t *testing.T) {
 	root := "/tmp/workspace"
 	previousDir := SessionPreviousDirForCampaign(root, "forsaken", "2026-04-19")