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/neogit.lua

@@ -0,0 +1,25 @@
+vim.pack.add({ 
+    { src = 'https://github.com/NeogitOrg/neogit' },
+    { src = 'https://github.com/sindrets/diffview.nvim' },
+})
+
+require('neogit').setup({
+    -- disable_context_highlighting = true,
+    disable_commit_confirmation = true,
+    disable_insert_on_commit = false,
+    disable_signs = true,
+    integrations = { diffview = true, fz_lua = false },
+    auto_refresh = false,
+    console_timeout = 5000,
+    auto_show_console = false,
+    sections = {
+        stashes = {
+            folded = false,
+        },
+        recent = { folded = false },
+    },
+})
+
+vim.keymap.set({'n'}, '<leader>vn', '<cmd>Neogit kind=auto<cr>', { desc = 'Neogit' })
+vim.keymap.set({'n'}, '<leader>vN', '<cmd>Neogit kind=floating<cr>', { desc = 'Neogit' })
+