[Sync] adopt unified stow layout from the private repo

Mirrors the private dots tree at 900bdda: one shared base plus per-host
overlays, replacing the old flat .config/ layout (last synced 2026-06-28).

- packages: common/ gui/ wm/ lw/ fl/ + install.sh and bin/ tooling (dotsync,
  reconcile-hyde.sh)
- new README (layout, deploy order, HyDE dependency), plus ToDo.md and
  HYDE-UPDATE.md
- current HyDE waybar rig (layouts/, cava), pi agent extensions, claude/
  config, tmux, presenterm, aichat roles
- drops stale duplicates and generated cruft that should never have been
  tracked: the second top-level .pi/ copy, btop.log, zellij config.kdl.bak,
  fish_variables, nvim codecompanion.lua
- .pi/agent/auth.json is gitignored now; auth.json.example ships instead
- fl/ and wm/ hypr themes/ stay untracked (HyDE-generated per machine, per
  the root .gitignore)

common/.config/nvim/init.lua

@@ -0,0 +1,38 @@
+vim.g.base46_cache = vim.fn.stdpath "data" .. "/base46/"
+vim.g.mapleader = " "
+vim.opt.relativenumber = true
+
+-- bootstrap lazy and all plugins
+local lazypath = vim.fn.stdpath "data" .. "/lazy/lazy.nvim"
+
+if not vim.uv.fs_stat(lazypath) then
+  local repo = "https://github.com/folke/lazy.nvim.git"
+  vim.fn.system { "git", "clone", "--filter=blob:none", repo, "--branch=stable", lazypath }
+end
+
+vim.opt.rtp:prepend(lazypath)
+
+local lazy_config = require "configs.lazy"
+
+-- load plugins
+require("lazy").setup({
+  {
+    "NvChad/NvChad",
+    lazy = false,
+    branch = "v2.5",
+    import = "nvchad.plugins",
+  },
+
+  { import = "plugins" },
+}, lazy_config)
+
+-- load theme
+dofile(vim.g.base46_cache .. "defaults")
+dofile(vim.g.base46_cache .. "statusline")
+
+require "options"
+require "nvchad.autocmds"
+
+vim.schedule(function()
+  require "mappings"
+end)