0.10.1: inline images through tmux

Fix: inline (WezTerm/iTerm2) images now work through tmux. tmux forwards passthrough data without moving the real terminal's cursor first. So each image landed where tmux had last left the cursor, the cells it was meant to cover stayed blank, and emoji appeared to vanish.

Each image now goes through as one passthrough that carries its own cursor save, absolute move and restore, using the pane's offset from tmux. A focus-in after a tmux window switch or reattach draws every image again. New: the paneOffset option and tmuxPaneOffset(). PR #122.