[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/mpv/input.conf

@@ -0,0 +1,65 @@
+# Volume
+9 add volume -5
+0 add volume 5
+
+UP add volume 2
+DOWN add volume -2
+
+k add volume 2
+j add volume -2
+
+# Seek backward / forward
+LEFT seek -5
+RIGHT seek 5
+
+l seek 5 
+h seek -5
+
+# Bigger jumps
+Shift+LEFT seek -30
+Shift+RIGHT seek 30
+
+# Precise nudge (Shift+h/l): 1s exact seek
+H seek -1 exact
+L seek 1 exact
+
+# Playback speed
+= add speed 0.1
+- add speed -0.1
+BS set speed 1.0          # backspace resets to normal
+
+# Subtitle sync
+z add sub-delay -0.1      # subs earlier
+Z add sub-delay 0.1       # subs later
+
+# Chapters
+> add chapter 1
+< add chapter -1
+
+# A-B loop (moved off L to avoid the precise-nudge conflict)
+b ab-loop
+
+# Audio sync (mirrors the z/Z subtitle-delay pair)
+x add audio-delay -0.1    # audio earlier
+X add audio-delay 0.1     # audio later
+
+# Playlist nav (< / > are used for chapters)
+[ playlist-prev
+] playlist-next
+
+# Track cycling
+a cycle audio             # next audio track
+n cycle sub               # next subtitle track
+v cycle sub-visibility    # (default) toggle subs on/off
+
+# Loop current file (distinct from the b A-B loop)
+r cycle-values loop-file inf no
+
+# Screenshots
+s screenshot              # (default) with subs
+S screenshot video        # clean frame: no subs/OSD
+
+# Info overlays
+i script-binding stats/display-stats-toggle   # (default) stats HUD
+o show-progress                                # flash progress/OSD
+