docs(mobile): document the phone gestures, and translate the selection bar

The three fixes in this branch change what a tap and a long-press MEAN on a
phone, and add a UI surface with its own z-index — all of which this repo keeps
written down rather than discoverable only by reading the handlers.

- `docs/wiki/Mobile-Guide.md` (the published user manual): a new "Tapping, links
  and copying" section, and the long-prompt behaviour in the keyboard section
  where the existing scroll/tap rules live.
- `CLAUDE.md`: the touch-gesture invariants next to the scrollback/wheel material
  (why the caret line is the boundary rather than the tap intent; why all three
  selection guards exist), the overlay's new bottom bound alongside the
  single-source note, and the selection bar in the z-index registry — 900, above
  terminal content and the local-echo overlay and deliberately below floating
  agent windows so it can never cover their controls.
- `i18n.js`: zh-CN for the bar's `Copy` / `Line` / `Clear selection`. The bar is a
  SIBLING of `.xterm`, not a descendant, so `SKIP_SELECTOR` does not cover it and
  the entries actually apply.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/web/public/i18n.js

@@ -500,6 +500,11 @@
     'Respawn Blocked': '重生已阻止',
     'Task Complete': '任务完成',
     'Copied to clipboard': '已复制到剪贴板',
+    // Terminal touch-selection bar (long-press to select). The bar is a sibling of
+    // `.xterm`, not a descendant, so SKIP_SELECTOR does not cover it and these apply.
+    Copy: '复制',
+    Line: '整行',
+    'Clear selection': '清除选择',
     'Failed to copy': '复制失败',
     'Checking…': '正在检查…',
     'Starting…': '正在启动…',