don't fail if landlock is not available at runtime

add comment on why don't landlock the net process

fmt

missing include

don't fail if ~/Downloads doesn't exist

forgot to log the path for a unveil error code path

add landlock support on linux landlock is applied only to the ui process to drop fs access and in the fs process to limit where telescope can read/write files. The network process is more difficult to landlock because while in theory it doesn't need *any* fs access, in practice it needs to read (at least) files inside /etc/ for DNS to work.

improve unveil' error reporting

fix sandbox wrt XDG-style directories

[openbsd] allow creation of files in ~/Downloads

(process) network -> net rename

ask to save a page when it can't be rendered it's good for thing like images and text with weird encodings.

don't include <err.h>, use the compat layer

fix various warnings, no functional changes now that we have a bounch of -Wxxx flags during compilation, let's fix everything.

adjust fs sandbox: allow writing and creating stuff into ~/.telescope