fix: mobile terminal scroll in both normal mode and tmux

- Dual-mode touch scroll:
  - Normal mode: scroll .xterm-viewport directly when scrollHeight > clientHeight
  - Alternate screen (tmux/vim): send SGR 1006 mouse-wheel protocol data
    using cursor position so tmux knows which pane to scroll
- Add touch-action: none to .terminal-container to prevent browser gestures
- Lock both html and body overflow when terminal page is open on mobile
- Remove synthetic WheelEvent approach (xterm.js SmoothScrollableElement
  doesn't reliably handle synthetic events)

apps/web/src/styles.css

@@ -77,6 +77,7 @@ body {
 	color: var(--ink);
 }
 
+html.terminal-page-open,
 body.terminal-page-open {
 	overflow: hidden;
 }
@@ -3707,6 +3708,7 @@ a.nav-item,
 	padding: 0;
 	overflow: hidden;
 	position: relative;
+	touch-action: none;
 }
 
 /* xterm.js manages its own sizing */