feat(#29): branded home screen + cluster info banner (PR-a)

internal/cli/cluster.go

@@ -117,6 +117,8 @@ func runClusterInfo(
 	ingestorSAOverride string,
 	tokenExpiry int64,
 ) error {
+	p.Banner("tracebloc", "cluster diagnostics")
+
 	resolved, err := cluster.Load(cluster.KubeconfigOptions{
 		Path:      kubeconfigPath,
 		Context:   contextOverride,

internal/cli/root.go

@@ -80,6 +80,23 @@ what's planned next.`,
 	root.AddCommand(newClusterCmd())
 	root.AddCommand(newDatasetCmd())
 
+	// Bare `tracebloc` (no subcommand) renders a friendly home screen
+	// instead of cobra's raw usage dump. Subcommands and --help are
+	// unaffected — cobra dispatches those before this RunE runs.
+	root.RunE = func(cmd *cobra.Command, args []string) error {
+		if len(args) > 0 {
+			return cmd.Help() // an arg that wasn't a known subcommand
+		}
+		p := printerFor(cmd)
+		p.Banner("tracebloc", "declarative data ingestion for your cluster")
+		p.Section("Get started")
+		p.Infof("tracebloc dataset push ./data     — stage + ingest a dataset (guided if you omit flags)")
+		p.Infof("tracebloc cluster info            — check the CLI can reach your cluster")
+		p.Infof("tracebloc ingest validate f.yaml  — validate an ingest.yaml locally")
+		p.Hintf("Add --help to any command for the full flag list.")
+		return nil
+	}
+
 	return root
 }
 

internal/cli/root_test.go

@@ -28,6 +28,26 @@ func TestRootCmd_HelpMentionsBinary(t *testing.T) {
 	}
 }
 
+// TestRootCmd_HomeScreen: a bare `tracebloc` (no subcommand) renders
+// the branded home screen pointing at the key commands, rather than
+// erroring or dumping raw usage.
+func TestRootCmd_HomeScreen(t *testing.T) {
+	root := NewRootCmd(BuildInfo{Version: "test"})
+	var out bytes.Buffer
+	root.SetOut(&out)
+	root.SetErr(&out)
+	root.SetArgs([]string{})
+
+	if err := root.Execute(); err != nil {
+		t.Fatalf("bare root failed: %v\n%s", err, out.String())
+	}
+	for _, want := range []string{"tracebloc", "dataset push", "cluster info"} {
+		if !strings.Contains(out.String(), want) {
+			t.Errorf("home screen missing %q:\n%s", want, out.String())
+		}
+	}
+}
+
 // `completion` is auto-registered by cobra, but it's load-bearing
 // for shell autocomplete UX. Verify it's reachable so a future
 // refactor that accidentally disables it (e.g. by setting