per-project (dir) session save/load

[xparq]

https://www.gnu.org/software/emacs/manual/html_node/emacs/Saving-Emacs-Sessions.html

• set desktop mode on by default initially, just to learn its details faster, annd also to conserve (+ surprise me with) forgotten remote sessions
• --no-desktop for the $EDIT wrapper, if desktop saving is on by def.
• does it save search, recent files & other history lists, too?
• actually almost EVERYTHING that's not global cfg should be saved as session data! Chk what other people have done for this "chrooting", apart from switching entire home dirs (similarly to VSCode profile switching)