Move nvim config into nvim/ subdirectory

Prepare repo structure for storing multiple dotfile configs.

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

nvim/lua/plugins/session.lua

@@ -0,0 +1,10 @@
+return {
+  "folke/persistence.nvim",
+  event = "BufReadPre",
+  opts = {},
+  keys = {
+    { "<leader>qs", function() require("persistence").load() end, desc = "Restore session" },
+    { "<leader>ql", function() require("persistence").load({ last = true }) end, desc = "Restore last session" },
+    { "<leader>qd", function() require("persistence").stop() end, desc = "Stop session saving" },
+  },
+}