Fix submit button while editing prompts in Studio Code UI (#4123)

## Related issues

Fixes STU-1832
Follow up to #4094

## How AI was used in this PR

AI assisted



## Proposed Changes

In #4094 I menthioned that
there is an issue with "Send" button, but I approved the PR so the
reported issue was not noticeable enough:<br /><img width="216"
height="429" alt="Screenshot 2026-07-08 at 16 07 13"
src="https://github.com/user-attachments/assets/dff64e13-c817-4207-9d64-d44529cb5803"
/>

So addressing it here:
<img width="152" height="156" alt="Screenshot 2026-07-08 at 16 07 41"
src="https://github.com/user-attachments/assets/24bd1076-d2fd-49a5-b072-b2857f731c17"
/>
<img width="155" height="162" alt="Screenshot 2026-07-08 at 16 07 55"
src="https://github.com/user-attachments/assets/da8de5fa-39a3-430a-8cd0-27b69fabc8f6"
/>

## Testing Instructions
Visual review should suffice, but JIC:
1. Navigate to the Studio Code tab and send a message
2. Pause the message before the AI had a chance to respond
3. Assert that "Send" button looks good.

Author: nightnei

apps/studio/src/components/studio-code-session/conversation/style.module.css

@@ -142,7 +142,8 @@
 	background-color: var(--color-frame-surface);
 }
 
-.userEditSendButton {
+/* Doubled class outweighs Tailwind preflight's `[type='button'] { background-color: transparent }` reset. */
+.userEditSendButton.userEditSendButton {
 	appearance: none;
 	border: none;
 	background-color: var(--color-frame-theme);