[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)

gui/.config/hypr/hyprlock-host.conf

@@ -0,0 +1,9 @@
+# Default (empty) per-host hyprlock sizes — fallback shared by all GUI hosts.
+# The real one comes from the per-host overlay (see lw/.config/hypr/hyprlock-host.conf).
+# Present so `source = ~/.config/hypr/hyprlock-host.conf` in hyprlock.conf always resolves,
+# even mid-install before the host overlay is stowed. A missing `source` target is a hard
+# parse error in hyprlang — for hyprlock that means the lock screen itself fails, so this
+# file must never be deleted.
+#
+# gui's defaults are tuned for wm (3072x1728 logical). To override, redefine any of:
+#   $fsClock  $fsDate  $fsMeta  $fsSmall  $fsIcon  $logoSize