[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/waybar/modules/battery.jsonc

@@ -0,0 +1,14 @@
+    "battery": {
+        "states": {
+            "good": 95,
+            "warning": 30,
+            "critical": 20
+        },
+        "format": "{icon} {capacity}%",
+        "rotate": ${r_deg},
+        "format-charging": " {capacity}%",
+        "format-plugged": " {capacity}%",
+        "format-alt": "{time} {icon}",
+        "format-icons": ["󰂎", "󰁺", "󰁻", "󰁼", "󰁽", "󰁾", "󰁿", "󰂀", "󰂁", "󰂂", "󰁹"]
+    },
+