fix(mobile): Keep custom answers owned by the displayed request#7

What Changed

A custom answer typed into a pending question on mobile is saved only to the request currently on screen, for the thread and environment currently on screen. Keystrokes that arrive after switching threads or environments, or after the question view unmounts, are dropped instead of being written elsewhere.

Why

The answer handler looked up the request by ID from a list that could belong to a different thread by the time it ran. Two threads, or two environments, can have requests with the same ID, so a late keystroke could land in the wrong draft answer. The handler now checks the displayed request, thread ID and environment ID together.

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes
• I included a video for animation/interaction changes