fix(thinkpad): ready the host for its first install

The host still carried snapper, which the desktop dropped in d3cc03c:
disk.nix creates no .snapshots subvolumes, so the timer would fail every
hour without ever taking a snapshot. The account sat in the docker group
while docker itself was off, and stateVersion named 26.05 although the
machine is first installed on 26.11.

Also drops the stale snapper mentions elsewhere and adds git-firefly to
Zed's auto-installed extensions.

modules/zed.nix

@@ -69,6 +69,7 @@ let
       "auto_install_extensions": {
         "catppuccin": true,
         "dockerfile": true,
+        "git-firefly": true,
         "html": true,
         "log": true,
         "nix": true,