remove nixpkgs less defaults and manage PAGER myself

this lets me avoid the lesspipe cross failures, notably

hosts/common/polyunfill.nix

@@ -13,7 +13,7 @@
     "/run/current-system/sw"
   ];
 
-  # NIXPKGS_CONFIG defaults to "/etc/nix/nixpkgs-config.nix", for idfk why.
+  # NIXPKGS_CONFIG defaults to "/etc/nix/nixpkgs-config.nix" in <nixos/modules/programs/environment.nix>.
   # that's never existed on my system and everything does fine without it set empty (no nixpkgs API to forcibly *unset* it).
   environment.variables.NIXPKGS_CONFIG = lib.mkForce "";
   # XDG_CONFIG_DIRS defaults to "/etc/xdg", which doesn't exist.
@@ -42,4 +42,10 @@
   # so as to inform when trying to run a non-nixos binary?
   # IMO that's confusing: i thought /lib/ld-linux.so was some file actually required by nix.
   environment.stub-ld.enable = false;
+
+  # `less.enable` sets LESSKEYIN_SYSTEM, LESSOPEN, LESSCLOSE env vars, which does confusing "lesspipe" things, so disable that.
+  # it's enabled by default from `<nixos/modules/programs/environment.nix>`, who also sets `PAGER="less"` and `EDITOR="nano"` (keep).
+  programs.less.enable = lib.mkForce false;
+  environment.variables.PAGER = lib.mkOverride 900 "";  # mkDefault sets 1000. non-override is 100. 900 will beat the nixpkgs `mkDefault` but not anyone else.
+  environment.variables.EDITOR = lib.mkOverride 900 "";
 }

hosts/common/programs/assorted.nix

@@ -62,6 +62,7 @@ in
       # "iw"
       "jq"
       "killall"
+      "less"
       # "libcap_ng"  # for `netcap`
       "lsof"
       # "miniupnpc"

hosts/common/programs/default.nix

@@ -53,6 +53,7 @@
     ./kdenlive.nix
     ./komikku.nix
     ./koreader
+    ./less.nix
     ./libreoffice.nix
     ./lemoa.nix
     ./loupe.nix

hosts/common/programs/less.nix

@@ -0,0 +1,6 @@
+{ ... }:
+{
+  sane.programs.less = {
+    env.PAGER = "less";
+  };
+}