fix(maestro): reliable touch scrollback on mobile

xterm's native touch scrolling crawled a line at a time and stalled after a
few. Map finger drags on the viewport to term.scrollLines (skipped on the alt
screen, which the app owns) and claim vertical pans via touch-action: pan-y.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/src/styles.css

@@ -1148,6 +1148,9 @@ textarea {
 .attach-body .xterm .xterm-viewport {
   overflow-y: auto;
   scrollbar-width: none;
+  /* We drive scrollback from touchmove (see attach.ts); claim vertical pans so
+     the browser doesn't fight the handler or trigger gestures mid-scroll. */
+  touch-action: pan-y;
 }
 
 .attach-body .xterm .xterm-viewport::-webkit-scrollbar {