chore(config): switch editor aliases to nvim and update related settings

dot_config/fish/conf.d/10-env.fish

@@ -17,6 +17,9 @@ set -gx EGET_BIN $HOME/.local/bin
 set -gx GHQ_ROOT $HOME/Code
 set -gx CODE_ROOT $HOME/Code
 
+set -gx EDITOR nvim
+set -gx VISUAL nvim
+
 # Go env (GOPATH/GOBIN) is pinned in ~/.config/mise/config.toml [env] because
 # mise's fish hook re-applies env each prompt and would clobber a shell-set
 # GOBIN. GOROOT is provided by mise (toolchain under ~/.local/share/mise).