[Sync] replace the flat layout with the unified stow tree

Supersedes the old flat .config/ layout (last published 2026-06-28) with the
private repo's structure: one shared base plus per-host overlays.

- packages: common/ gui/ lw/ fl/ wm/ plus install.sh and bin/ tooling
  (dotsync, reconcile-hyde.sh)
- new README covering the layout, deploy order and the HyDE dependency
- current HyDE waybar rig (layouts/, cava), pi agent extensions, claude/
  config, tmux, presenterm, aichat roles
- fish: kp (keepassxc-cli + fzf picker, db path from $KP_DB) and
  bind_M_n_history (alt+1..9 recalls the nth history entry)
- drops cruft that should never have been tracked: the duplicate top-level
  .pi/ copy, btop.log, zellij config.kdl.bak, fish_variables
- .pi/agent/auth.json is gitignored; auth.json.example ships instead

Host-specific work sessions and the personal backlog stay in the private
tree. Endpoint locators in the llamacpp/whisper guides are placeholders
($SERVER, <own-domain>) — the guides themselves stay, since they are the
useful part.

gui/.config/fish/conf.d/waybar.fish

@@ -0,0 +1,8 @@
+## gui package — waybar helpers. Lives in conf.d/ (fish sources every conf.d/*.fish),
+## NOT in host.fish: each host package ships its own host.fish, which stow deploys last
+## with --override — a gui/host.fish would be shadowed on every host that has one.
+
+# Reload the custom waybar (kill + relaunch, detached so it survives this shell).
+# Same invocation as userprefs.conf exec-once / the Ctrl+Alt+W bind. Killing waybar
+# also stops its cava child (cava-waybar.sh is a child of the bar).
+abbr wbar 'killall waybar; setsid -f waybar -c ~/.config/waybar/layouts/custom.jsonc -s ~/.config/waybar/layouts/custom.css'