[striga] link bank UI fixes (#22577)

## Overview

- minor fixes for the link bank UI and copy changes

## Test Plan

![Screenshot 2025-12-16 at 2.59.21 PM.png](https://app.graphite.com/user-attachments/assets/cbbe3bd3-a8ce-4a20-9896-e0370508ecb3.png)

![Screenshot 2025-12-16 at 2.59.09 PM.png](https://app.graphite.com/user-attachments/assets/9be54352-cfb0-4b07-bba7-446a934d30de.png)

![Screenshot 2025-12-16 at 3.05.17 PM.png](https://app.graphite.com/user-attachments/assets/b440d147-4446-4bbd-af36-b4fa28534aff.png)

![Screenshot 2025-12-16 at 3.00.47 PM.png](https://app.graphite.com/user-attachments/assets/51ccb0ac-d951-4648-bbff-269eeb46dce9.png)

GitOrigin-RevId: 7c380f30fe882496802e22fee1f1480348c20f35

Author: bsiaotickchong

packages/ui/src/components/Flex.tsx

@@ -37,7 +37,7 @@ type FlexProps = {
     | "pre-line"
     | undefined;
   height?: number | "auto" | "100%" | undefined;
-  width?: number | "auto" | "100%" | undefined;
+  width?: number | "auto" | "50%" | "100%" | undefined;
   mt?: number | "auto" | undefined;
   mr?: number | "auto" | undefined;
   mb?: number | "auto" | undefined;