Add opt-in theme sync to herdr machines (#13430)

* Add a theme-set sample hook that mirrors themes to herdr machines

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Mirror theme changes to herdr machines by default

Replaces the sample hook with omarchy-theme-sync, which omarchy-theme-set
starts detached after every theme change, and a theme-sync-off toggle that
stops a machine from both sending and receiving.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Rename omarchy-theme-sync to omarchy-theme-set-herdr-machines

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Label the toggle Herdr Theme Sync and extract its menu guard

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Answer the Herdr Theme Sync menu guard from omarchy-theme-set-herdr-machines

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Sync herdr machines one at a time and drop the dry run

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Check the theme sync toggle under the lock and stop special-casing this machine

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Make herdr theme sync opt-in

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

docs/theming.md

@@ -45,6 +45,8 @@ Making a new app follow theme changes means adding its restart/retint command
 to that list. Runs serialize on a `flock`, so scripted theme changes queue
 instead of racing.
 
+Last, it starts `omarchy-theme-set-herdr-machines` detached. That command sets the same theme on every enabled `herdr machine list` target that runs Omarchy, over SSH inside the remote's live Hyprland session, and logs each machine's result to `~/.local/state/omarchy/theme-set-herdr-machines.log`. Sync is off by default. The `herdr-theme-sync` toggle turns it on, and a machine only sends and accepts themes while it is on. A mirrored change carries `OMARCHY_THEME_SYNC_FROM`, so the receiving machine never sends it on.
+
 ## What an installed theme may not ship
 
 `themes/<name>/` in this repo is Omarchy's own code and is trusted. So is a theme the user wrote by hand in `~/.config/omarchy/themes/<name>/`: it is their machine and their file, and both stage in full.