Fix relative path issues in installer and bindings

[2color]

Use realpath to ensure absolute paths when creating symlinks
and sourcing scripts, preventing broken symlinks when invoked
from different directories.

[ibehnam]

Thanks! shellock_bindings.fish already resolves its path via realpath, but install.fish still used dirname (status filename). I’ve updated install.fish on main to use dirname (realpath (status filename)) and confirmed installs work both directly and via a symlinked installer. So the remaining value is in the installer path fix; bindings change is redundant on main.