[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/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