fix(dashboard): lock ChatView composer with touch-action: none on textarea

A pan-y gesture on the focused textarea still triggered iOS auto-
scroll-into-view, lifting the composer up off-screen even with body
locked. touch-action: none on .chat-input-textarea blocks gesture-
driven panning entirely (tap-to-focus, typing, caret moves still
work) so the composer stays anchored. Trade-off: loses gesture-
scroll within the textarea once content exceeds max-height — minor
since textareas rarely exceed 6 lines in this composer.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/dashboard/app/components/ChatView.css

@@ -848,11 +848,14 @@
   line-height: 1.4;
   max-height: 120px;
   min-height: 40px;
-  /* iOS: a vertical swipe started on the textarea otherwise rubber-bands
-     the document, momentarily exposing the body background. pan-y keeps
-     internal multi-line scroll usable while preventing the gesture from
-     escaping to the page. */
-  touch-action: pan-y;
+  /* iOS: any pan-y gesture on the textarea (including pan-y itself)
+     can drive an auto-scroll-into-view that lifts the composer up
+     off-screen even with body locked. touch-action: none blocks
+     gesture-driven panning while keeping tap-to-focus and typing
+     intact. Trade-off: loses gesture scroll within the textarea once
+     content exceeds max-height (~6 lines); arrow keys / caret moves
+     still work. */
+  touch-action: none;
   overscroll-behavior: contain;
 }