Ssh, disable DefaultConfig to supress warning

This merges all the different files into one app.nix using nixvim
instead of the manual home-manager nvim management.

Behavior should be almost unchanged, with the following changes:
- Plugins now have defaults for my own personal sane default experience
- The highlighted line is now 80 instead of 81
- Treesitter plugins may not be integrated correctly

hmModules/apps/neovim/app.nix

@@ -68,11 +68,11 @@
         smartcase = true;
       };
 
-      keymaps = with config.lib.nixvim; [
+      keymaps = [
         {
           key = "<leader>d";
           mode = "n";
-          action = mkRaw "vim.diagnostic.open_float";
+          action = "vim.diagnostic.open_float()";
         }
         # -- Easy Split Navigation
         # -- nnoremap <C-J> <C-W><C-J>
@@ -111,19 +111,49 @@
       cmp = {
         enable = nvimcmp.enable;
         autoEnableSources = true;
-          settings = {
-            sources = [
+        settings.sources = [
           { name = "nvim_lsp"; }
           { name = "path"; }
           { name = "buffer"; }
         ] ++ lib.optional luasnip.enable { name = "cmp-luasnip"; };
 
-          mapping = with config.lib.nixvim; {
-            "<C-Space>" = mkRaw "cmp.mapping.abort()";
-            "<Tab>" = mkRaw
-              "cmp.mapping(cmp.mapping.select_next_item(), {'i', 's'})";
-            "<S-Tab>" = mkRaw
-              "cmp.mapping(cmp.mapping.select_prev_item(), {'i', 's'})";
+        mapping = {
+          "<C-Space>" = "cmp.mapping.complete {}";
+          "<CR>" = "cmp.mapping.confirm {
+            behavior = cmp.ConfirmBehavior.Replace,
+            select = true,
+          }";
+          "<Tab>" = {
+            actions = ''
+              function(fallback)
+                if cmp.visible() then
+                  cmp.select_next_item()
+            '' + lib.optionalString luasnip.enable ''
+                elseif luasnip.expand_or_locally_jumpable() then
+                  luasnip.expand_or_jump()
+            '' + ''
+                else
+                  fallback()
+                end
+              end
+            '';
+            modes = [ "i" "s" ];
+          };
+          "<S-Tab>" = {
+            actions = ''
+              function(fallback)
+                if cmp.visible() then
+                  cmp.select_prev_item()
+            '' + lib.optionalString luasnip.enable ''
+                elseif luasnip.locally_jumpable(-1) then
+                  luasnip.jump(-1)
+            '' + ''
+                else
+                  fallback()
+                end
+              end
+            '';
+            modes = [ "i" "s" ];
           };
         };
       };
@@ -149,7 +179,7 @@
         enable = treesitter.enable;
         highlight.enable = true;
         indent.enable = true;
-        folding.enable = false;
+        folding.enable = true;
       };
 
       vimwiki = {