## What changed
Add the `› ` prefix to pinned prompt headers, using bold red for spoken prompts and bold dim styling for other prompts. Reserve one column when truncating the header.
## Testing
Add a rendering test comparing pinned headers with the original prompt rows for both regular and spoken prompts. Update snapshots for the prefix and display-width truncation.
GitOrigin-RevId: 89c2d9267374ef8f6504058c12c078025f302fef