[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/mappings.lua

@@ -0,0 +1,25 @@
+require "nvchad.mappings"
+
+-- add yours here
+
+local map = vim.keymap.set
+
+map("n", "gd", vim.lsp.buf.definition, { desc = "Go to definition" })
+map("n", "gD", "<cmd>Telescope lsp_definitions<CR>", { desc = "Go to Definitions" })
+map("n", "grr", "<cmd>Telescope lsp_references<CR>", { desc = "Go to references" })
+map("n", "<leader>da", ":lua vim.lsp.buf.code_action()<cr>", { desc = "Code actions", noremap = true, silent = true })
+map("n", "<leader>dh", ":lua vim.diagnostic.open_float()<CR>", { desc = "Show diagnostics" })
+map("n", "<leader>dj", function()
+  vim.diagnostic.jump { count = 1, float = true }
+end, { desc = "Go to next" })
+map("n", "<leader>dk", function()
+  vim.diagnostic.jump { count = -1, float = true }
+end, { desc = "Go to previous" })
+-- Telescope
+map("n", "<leader>fr", ":Telescope resume<CR>", { desc = "Resume last search" })
+map("n", "<leader>fs", ":Telescope grep_string<CR>", { desc = "Find selected string" })
+map("n", "<leader>fk", ":Telescope keymaps<CR>", { desc = "Find keymaps" })
+map("n", "<leader>fd", ":Telescope diagnostics<CR>", { desc = "Diagnostics" })
+-- Remaps
+map({ "n", "v" }, "x", '"_x', { desc = "Delete char without yanking" })
+map({ "n", "v" }, "c", '"_c', { desc = "Change without yanking" })