Swapping between pull requests in webview does not clear text box

[joshspicer]

Testing #6832

1. Open one pull request in webview
2. Type something in a box but do not submit
3. Swap to a different pull request

Screen.Recording.2025-04-29.at.11.43.54.AM.mov

I think the best experience would be that the in-progress text is remembered per webview