Update eca-webview: restore chat vertical scroll

Bump eca-webview to 510f68b ("Fix chat scroll: lock .message-row height
inside flex-column scroller"). The .message-row { overflow: hidden }
rule introduced in a recent webview update collapsed each row's
automatic min-height to 0 (CSS Flexbox §4.5), letting flex-shrink
compress and crop messages instead of overflowing into the chat
scroller. flex-shrink: 0 restores natural row heights so the
.messages-container scroller behaves as intended.

🤖 Generated with [eca](https://eca.dev)

Co-Authored-By: eca-agent <git@eca.dev>

Author: ericdallo