Fixes across the chat layer and the Ask composer.

The chat no longer jumps back to the bottom while you scroll up during a streaming reply. It follows new messages only when you are already at the bottom.
The transcript no longer blinks or briefly clears when the conversation reloads. What could look like another chat flashing by was old history replayed during those reloads, fixed by the same change.
Skill instructions and other text injected by Claude Code no longer show up as if you had typed them.
The Terminal tab at the top right now really switches to the terminal, and the agent tab switches back to chat.
The stop button was removed from the chat input so a mistimed click can no longer interrupt the agent. Stop stays available in the session menu and on ⌘.
Typing and pasting very large prompts in the Ask composer is much faster.
Starting a session with a very large prompt now works. Prompts over about 14 KB used to fail silently before Claude could launch.