feat: the right pane describes what's selected in the pane you're in

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

internal/ui/app/notes_test.go

@@ -42,7 +42,7 @@ func TestNotesOnRows(t *testing.T) {
 	d.note("main prod")
 
 	screen := d.screen()
-	for _, want := range []string{"stripe live", "app secrets", "main prod", "note       stripe live"} {
+	for _, want := range []string{"stripe live", "app secrets", "main prod", "note       main prod"} {
 		if !strings.Contains(screen, want) {
 			t.Errorf("missing %q:\n%s", want, screen)
 		}