fix(tmux): use SurfaceView for all tmux notification objects

Convert STATE_CHANGED, EXIT, READY, and COMMAND_RESPONSE handlers to
extract SurfaceView from ghostty_surface_userdata instead of posting
the raw ghostty_surface_t. This makes multi-surface identity filtering
consistent across all tmux notifications — the 'as? SurfaceView' cast
in SSHSession observers now succeeds for these older handlers too.

Also removes emoji from log messages per established convention.