OmaSession 0.5.1

• omarchy plugin add ... --enable is now the whole install. The plugin declares a service that the shell starts once, and it sets up the snapshot timer and the login restore line that used to need a separate omasession install. It runs at every shell start and changes only what is missing or out of date. A login line you deleted stays deleted, a timer you disabled in systemd stays off, and nothing is set up again after omasession uninstall, including when those were done under 0.5.0. Requested in the Omarchy plugin marketplace review.
• A disabled plugin no longer saves or restores. The timer now runs save --if-enabled, and the login restore checks the same thing: whether omarchy-shell has the plugin enabled. The manual commands still work.
• After omarchy plugin remove without uninstall, the timer and the login line are inert instead of failing. Both units carry ConditionPathExists, and the login line checks that the CLI exists. A line written by an earlier version gets that check in place, keeping the path it names.
• The login restore runs once per Hyprland instance. A second login line in autostart.lua, such as one for a development checkout next to the installed plugin, does nothing.
• The panel says when automatic save is off: the plugin is not enabled, or the snapshot timer is not running.

This release is tagged at commit 04ca2658f23a02739b6aad5e3a893ee33f0b5178.