Sign In Template appends username to password

Whenever a username is entered it will also be displayed in the password input field. It can't be removed and it even stays when going back to the username template.

Search the repository for the Sign In Template entry point and reproduce the issue by entering a username, checking the password field, and navigating back. Trace the template's input and navigation state, then verify that the password field never displays or retains the username across navigation.

Written by the indexing model from the issue text.