Move the fields section out of the composer's scroll container so it
stays visible while scrolling long bodies, matching the pinned
formatting toolbar. Since the fields were the first child of the
scroll container, hoisting them above it is visually identical to
making them sticky - but needs no dynamic offset for the toolbar's
own sticky top (the fields' height varies with Cc/Bcc toggling and
recipient-chip wrapping). The scroll container now wraps only the
body and the signature preview.
Co-Authored-By: Claude <noreply@anthropic.com>