[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/lua/chadrc.lua

@@ -0,0 +1,57 @@
+-- This file needs to have same structure as nvconfig.lua
+-- https://github.com/NvChad/ui/blob/v3.0/lua/nvconfig.lua
+-- Please read that file to know all available options :(
+
+---@type ChadrcConfig
+
+local M = {
+  lsp = { signature = true },
+
+  base46 = {
+    theme = "onedark",
+    transparency = true,
+    hl_override = {
+      NvimTreeGitDirty = {
+        fg = "#DBA55D",
+      },
+    },
+    -- Comment = { italic = true },
+    -- ["@comment"] = { italic = true },
+  },
+
+  nvdash = {
+    load_on_startup = true,
+    -- buttons = {
+    --   { txt = "  Find File", keys = "Spc f f", cmd = "Telescope find_files custom" },
+    --   { txt = "  Recent Files", keys = "Spc f o", cmd = "Telescope oldfiles" },
+    --   -- more... check nvconfig.lua file for full list of buttons
+    -- },
+  },
+
+  ui = {
+    -- lazyload it when there are 1+ buffers
+    tabufline = {
+      enabled = true,
+      lazyload = true,
+      order = { "treeOffset", "buffers", "tabs", "btns" },
+      modules = nil,
+      bufwidth = 21,
+    },
+  },
+
+  term = {
+    base46_colors = true,
+    winopts = { number = false },
+    sizes = { sp = 0.5, vsp = 0.2, ["bo sp"] = 0.3, ["bo vsp"] = 0.2 },
+    float = {
+      relative = "editor",
+      row = 0.05,
+      col = 0.05,
+      width = 0.9,
+      height = 0.8,
+      border = "single",
+    },
+  },
+}
+
+return M