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/favourites_test.go

@@ -421,8 +421,9 @@ func TestStarIsPerAccount(t *testing.T) {
 	d.keys("n")
 	d.typeText("shared note")
 	d.keys("enter")
-	if n := strings.Count(d.screen(), "shared note"); n != 2 {
-		t.Errorf("note shown %d times, want 2:\n%s", n, d.screen())
+	// On both accounts' rows, and in the selected one's details.
+	if n := strings.Count(d.screen(), "shared note"); n != 3 {
+		t.Errorf("note shown %d times, want 3:\n%s", n, d.screen())
 	}
 	d.keys("F")
 	var labels []string