[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.

common/.config/fish/functions/copy-commandline.fish

@@ -0,0 +1,18 @@
+function copy-commandline
+    set -l cmd (commandline)
+    if test -n "$cmd"
+        if type -q pbcopy
+            echo -n "$cmd" | pbcopy
+        else if type -q xclip
+            echo -n "$cmd" | xclip -selection clipboard
+        else if type -q wl-copy
+            echo -n "$cmd" | wl-copy
+        end
+        
+        # Provide brief visual feedback in the prompt
+        set -l original_cmd (commandline)
+        commandline -r "Copied!"
+        sleep 0.4
+        commandline -r "$original_cmd"
+    end
+end