Harden markdown-row settle until formatted heading paints

The formatted-markdown settle predicate treated a missing "## Title"
as formatted. A frame that had painted the link URL but not the
heading yet satisfied that check and then failed toContain("Title").

The ###-heading test already requires the formatted body for the
same reason.

Author: TheGreatAxios

src/tui/markdown-rows.test.ts

@@ -73,7 +73,15 @@ describe("markdown transcript rows", () => {
 
       const frame = await settle(
         h,
-        (f) => f.includes("docs") && !f.includes("## Title") && !f.includes("**bolded**"),
+        // Require formatted heading and bold: "docs" plus absence of "## Title"
+        // can match a frame where the heading has not painted yet (same class as
+        // the ### heading flake below).
+        (f) =>
+          f.includes("Title") &&
+          f.includes("bolded") &&
+          f.includes("docs") &&
+          !f.includes("## Title") &&
+          !f.includes("**bolded**"),
       );
       expect(frame).toContain("Title");
       expect(frame).not.toContain("## Title");