refactor(config/nvim): move pack.add declarations into individual plugin files

The monolithic vim.pack.add() table in init.lua was removed and each
plugin/*.lua file now declares its own dependencies via vim.pack.add()
at the top. tools.lua was decomposed into per-plugin files (cmake.lua,
jupynvim.lua, just.lua, kulala.lua, mise.lua, neogit.lua, sshfs.lua,
trouble.lua, undotree.lua, zoxide.lua) each with their own config and
keymaps. This makes plugin files self-contained and easier to maintain.

config/nvim/plugin/sshfs.lua

@@ -0,0 +1,14 @@
+
+vim.pack.add({
+    { src = 'https://github.com/uhs-robert/sshfs.nvim' },
+})
+
+require('sshfs').setup({
+    mounts = {
+        base_dir = vim.fn.expand("$HOME") .. "/Public", -- where remote mounts are created
+    },
+    lead_prefix = "<leader>t",     
+    -- Refer to the configuration section below
+    -- or leave empty for defaults
+})
+