feat: add gx.nvim, comment-box, and machine-local override support

- Add gx.nvim for smart URL opening (GitHub, plugins, package.json, search)
- Add comment-box.nvim with keymaps for creating/deleting comment boxes
- Load machine-local secrets.lua and local.lua from ~/.config/.user-dots/nvim/
- Update README with new plugins, keymaps, and portability highlight

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lua/keymaps.lua

@@ -322,6 +322,14 @@ vim.keymap.set("n", "<leader>uu", "<cmd>UndotreeToggle<cr>", { desc = "Toggle Un
 
 ----------------------------------------------------------
 
+-- Comment Box Keymaps
+vim.keymap.set({ "n", "v" }, "<leader>cbb", "<cmd>CBccbox<cr>", { desc = "Centered Box" })
+vim.keymap.set({ "n", "v" }, "<leader>cbl", "<cmd>CBcline<cr>", { desc = "Centered Line" })
+vim.keymap.set({ "n", "v" }, "<leader>cbd", "<cmd>CBd<cr>", { desc = "Delete Box/Line" })
+vim.keymap.set("n", "<leader>cbk", "<cmd>CBcatalog<cr>", { desc = "Box Style Catalog" })
+
+----------------------------------------------------------
+
 -- Persistence Keymaps
 vim.keymap.set("n", "<leader>qs", function()
 	require("persistence").load()

lua/plugins.lua

@@ -102,7 +102,14 @@ Config.plugins.snacks = {
 		enabled = true,
 		win = {
 			keys = {
-				toggle = { "<c-/>", function(self) self:hide() end, mode = "t", desc = "Toggle Terminal" },
+				toggle = {
+					"<c-/>",
+					function(self)
+						self:hide()
+					end,
+					mode = "t",
+					desc = "Toggle Terminal",
+				},
 			},
 		},
 	},
@@ -172,6 +179,21 @@ lazyload.on_vim_enter(function()
 	vim.pack.add({ { src = "https://github.com/echasnovski/mini.pairs", name = "mini.pairs" } })
 	require("mini.pairs").setup()
 
+	-- Gx.nvim
+	vim.pack.add({ { src = "https://github.com/chrishrb/gx.nvim", name = "gx" } })
+	require("gx").setup({
+		handlers = {
+			plugin = true,
+			github = true,
+			package_json = true,
+			search = true,
+		},
+	})
+
+	-- Comment-box.nvim
+	vim.pack.add({ { src = "https://github.com/LudoPinelli/comment-box.nvim", name = "comment-box" } })
+	require("comment-box").setup()
+
 	-- Undotree
 	vim.g.undotree_ShortIndicators = 0
 	vim.g.undotree_SplitWidth = 32