fix: route mobile terminal swipes to the terminal, not the page layout

- Add touch-action: none and overscroll-behavior: none to mobile terminal
  page, content, wrapper, container, and xterm viewport so the browser
  never treats swipes as page/address-bar scrolling or pull-to-refresh.
- Make .terminal-page.mobile fixed-position to prevent viewport layout
  scroll; keep the overlay toolbar as absolute with pointer-events only
  on interactive parts.
- Rework the mobile touch handler in terminal.tsx:
  * Detect normal vs alternate buffer via term.buffer.active.type instead
    of measuring the DOM viewport, which was unreliable in tmux/vim.
  * Accumulate swipe distance and emit SGR 1006 mouse-wheel sequences in
    steps, so tmux pane scrolling tracks the gesture correctly.
  * Prevent default as soon as the swipe is recognized so the page does
    not start a competing scroll gesture.

Quality gates: npm run typecheck, npm run lint clean, npm test -- --run 87 passed.

apps/web/.pi-map.index.md

@@ -2,7 +2,7 @@
 dir: apps/web
 
 ## role
-Frontend web application providing a browser-based React/TypeScript UI with code editing, terminal, and routing capabilities.
+Frontend web application providing a browser-based UI with code editing, terminal, and routing capabilities for the "headquarter" project.
 ## parent
 index: apps/.pi-map.index.md
 map: apps/.pi-map.md