fix: copy-mode support for edit and recent capture

[KapJI]

Fixes two copy-mode issues:

• edit now works when the target pane is in copy mode.
• @extrakto_grab_area set to recent/window recent now captures the current copy-mode viewport, not the pane tail.

Implementation uses display-message formats (pane_in_mode, scroll_position, pane_height) to compute capture bounds.
I did not use capture-pane -M because it is only available in tmux 3.6+, while tmux 3.5a is still widely used. E.g. latest Debian Trixie has it.

[laktak]

Thanks for your PR! I did not see any side effects, at least on my setup, so I'll merge it as it is.

The fallback is good even though I don't like that it eats all errors, making it impossible to diagnose any issues with it. I guess I'll add a debug switch if it is needed.