nixvim: improve keymaps, completion, and formatter config

- Add LSP code actions, diagnostic navigation, window navigation keymaps
- Move telescope keymaps to explicit mkRaw form for reliability
- Change buffer nav from <leader>bh/bl to [b/]b
- Fix conform double-setup by moving config to native nixvim settings
- Fix <leader>cf to use conform instead of vim.lsp.buf.format
- Fix <leader>ca to pass diagnostic context to code_action
- Add nvim-lightbulb for code action indicator
- Configure copilot Tab conflict: blink-cmp Tab=accept, C-n/p for cycling
- Add completion.list.selection preselect for immediate Tab acceptance
- Add TypeScript Japanese locale for LSP diagnostics

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

modules/home/nixvim/plugins/editor/telescope.nix

@@ -1,43 +1,6 @@
 {...}: {
-  programs.nixvim = {
-    plugins.telescope = {
-      enable = true;
-      extensions = {
-        fzf-native.enable = true;
-      };
-      keymaps = {
-        "<leader>ff" = {
-          action = "find_files";
-          options = {
-            desc = "ファイルを探す";
-            silent = true;
-          };
-        };
-
-        "<leader>fg" = {
-          action = "live_grep";
-          options = {
-            desc = "文字列を全文検索";
-            silent = true;
-          };
-        };
-
-        "<leader>fb" = {
-          action = "buffers";
-          options = {
-            desc = "開いているバッファを探す";
-            silent = true;
-          };
-        };
-
-        "<leader>fh" = {
-          action = "help_tags";
-          options = {
-            desc = "ヘルプ項目を探す";
-            silent = true;
-          };
-        };
-      };
-    };
+  programs.nixvim.plugins.telescope = {
+    enable = true;
+    extensions.fzf-native.enable = true;
   };
 }