Install Elsewhen, the world clock plugin, by default

Elsewhen (omacom.elsewhen) arrives as the elsewhen package under
/usr/share/omarchy/plugins, the packaged root the shell scans between its
bundled plugins and the user's. It opens the right section of the default
bar, just before the tray, and a migration installs the package, writes the
widget into a customized shell.json in the same spot, and retires a pristine
pre-package clone of the upstream repo that the package now shadows.

test/shell.d/config-test.sh

@@ -41,11 +41,12 @@ pass "default clock date format has no leading zero"
 jq -e '
   def ids: map(.id // .);
   (.bar.layout.right | ids) as $ids |
+  ($ids | index("omacom.elsewhen")) as $elsewhen |
   ($ids | index("omarchy.tray")) as $tray |
   ($ids | index("omarchy.agents")) as $agents |
-  $tray != null and $agents == $tray + 1
+  $elsewhen == 0 and $tray == 1 and $agents == $tray + 1
 ' "$ROOT/config/omarchy/shell.json" >/dev/null
-pass "default right layout keeps agents next to the tray"
+pass "default right layout opens with elsewhen and the tray, then agents"
 
 ROOT="$ROOT" python3 <<'PY'
 import json