Keep omarchy-system-logout, -reboot and -shutdown as compatibility names

Problem

Omarchy 4.0.6 shipped omarchy-system-logout, omarchy-system-reboot and omarchy-system-shutdown as visible commands, each with its own omarchy:summary. #15231 folded them into one omarchy-system <logout|reboot|shutdown> command and deleted the three files. It left no compatibility names behind.

The omarchy reboot and omarchy system reboot routes still work. Calling the command by its file name now fails:

$ OMARCHY_PATH=/usr/share/omarchy PATH=$OMARCHY_PATH/bin:/usr/bin
$ omarchy system reboot --help     # router: fine
Usage:
  omarchy system <logout|reboot|shutdown>
$ command -v omarchy-system-reboot || echo not found
not found

The file name is what users copied into their own configuration:

• o.bind(...) lines in ~/.config/hypr/bindings.lua
• menu extension rows in ~/.config/omarchy/extensions/omarchy-menu.jsonc (the 4.0.6 menu's own rows used "action":"omarchy-system-reboot")
• hooks and personal scripts

After the upgrade those calls print "command not found" and nothing happens.

Fix

Add three hidden shims, each exec omarchy-system <action> "$@". ShellCheck is clean.

Verify

bin/omarchy-system-reboot --help    # prints omarchy-system's usage
omarchy                             # the shims stay out of the listing (hidden)

test/cli should pass unchanged. Run it in CI.

Found while testing Omarchy 4.5.0-rc1.