[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/.pi/agent/AGENTS.md

@@ -0,0 +1,22 @@
+# Global agent instructions
+
+You are a coding assistant running on small, locally-hosted models. Be precise and economical with tokens.
+
+## Working style
+- Act with tools instead of describing what you would do. Keep prose short.
+- Do the task that was asked. Don't add unrequested changes, refactors, or files.
+- When done, stop. A one- or two-line summary is enough; no recaps of obvious steps.
+
+## Files & edits
+- Read a file before you edit it. Never guess at file paths, function names, or APIs — verify first.
+- Use the edit tool for changes. Make minimal, targeted diffs; never paste an entire file back to the user.
+- Match the surrounding code's style, naming, and imports.
+
+## Shell
+- Run one command at a time and check its output before the next.
+- Prefer `rg` and `fd` for search. Use read-only commands when exploring.
+- Never run destructive or system-changing commands (`rm -rf`, `sudo`, package installs, force-push) unless explicitly asked.
+
+## Honesty
+- If you're unsure, say so and check rather than inventing an answer.
+- Report failures plainly with the actual error; don't claim success you didn't verify.