[Bug]: Goal status and controls require scrolling to the end of long threads#25954

Goal status and controls sit at the end of the conversation. When I read earlier messages in a long thread, I have to scroll all the way down to see or use them. The goal is not hidden behind a panel.

Reproduction

1. Set a goal in a long thread.
2. Scroll up to read earlier messages.
3. Try to check the goal or use its controls without returning to the bottom.

Goal status and controls should remain accessible while reading the conversation.

Code and release status

In nightly 20261027.3770, ChatView passes the goal to ThreadNow, which renders it in the timeline footer. This is still the arrangement in main dc84b0962e.

The proposed fix places the existing goal item in the composer banner stack. An isolated 80-message fixture confirms that the controls remain beside the composer after scrolling up. In the original layout, the Resume button in the same scrolled view was below the 800 px viewport, at about 1,784 px.

The connected server is v0.1.2 on Ubuntu 24.04.5 x86_64. The reporter's browser build and version are unknown. Typography feedback remains separate in #25953.

Implementation PR: #26023. The change is proposed and has not shipped.