[FEATURE] Anchor the viewport at the TOP of each new response (read forward, not scroll back)

Problem: When Claude Code prints a long response, the viewport ends at the bottom of the output. To read it in order I have to scroll up to find where it began — and I often miss the top entirely.

What I want: When a response completes, park the view at the top of that response (right at my prompt), so I read forward top-to-bottom (space / page-down), then land back at the input to type my next prompt. Like opening a file in less: it starts at the top, not the bottom.

Why: Reading forward is natural and lossless; scrolling back is friction and I miss content. This is about viewport positioning, not scrollback capacity.

Suggested shape: a config toggle, e.g. settings.json → "responseAnchor": "top" (default keeps current bottom-anchor behavior).

Distinct from: the scrollback-destruction bugs (e.g. #42002) and scroll-jump bugs (e.g. #33367) — those are about losing history; this is about where the view sits after a completed turn.