[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)

common/.config/claude/keybindings.json

@@ -0,0 +1,36 @@
+{
+  "$schema": "https://www.schemastore.org/claude-code-keybindings.json",
+  "$docs": "https://code.claude.com/docs/en/keybindings",
+  "bindings": [
+    {
+      "context": "Global",
+      "bindings": {
+        "alt+j": "scroll:lineDown",
+        "alt+k": "scroll:lineUp",
+        "ctrl+shift+j": "scroll:lineDown",
+        "ctrl+shift+k": "scroll:lineUp"
+      }
+    },
+    {
+      "context": "MessageSelector",
+      "bindings": {
+        "g": "messageSelector:top",
+        "shift+g": "messageSelector:bottom"
+      }
+    },
+    {
+      "context": "Select",
+      "bindings": {
+        "g": "select:first",
+        "shift+g": "select:last"
+      }
+    },
+    {
+      "context": "Footer",
+      "bindings": {
+        "j": "footer:down",
+        "k": "footer:up"
+      }
+    }
+  ]
+}