[Extension Idea] Password Manager integration

# Description of the new feature/enhancement

An extension idea would be to allow for password manager integration, for example through the command pallette or a hotkey. After searching the entry to fill out (in a command pallette-alike dropdown with search) it would then fill out the username, password, or any other field. Some password managers like 1Password already have some form of desktop integration, but it's not excellent. Native incorporation in Windows Terminal would be amazing.

# Proposed technical implementation details (optional)

We will probably first need extension support for this, but then it should be relatively easy.

Start by investigating the extension support mentioned in the issue, then trace the command palette and hotkey entry points in Windows Terminal. Review how a password-manager search could select an entry and fill usernames, passwords, or other fields. Done means an agreed integration design and working native password-manager flow, but the issue does not identify files or tests.

Written by the indexing model from the issue text.