fixo::ScenePickerWidget

Remote-side widget that renders one button per published scene.

Detailed description

Subscribes to a `SyncSection` (typically the runtime's `"fixo-runtime"` section) and renders one push-button per scene declared at `scenes/<i>/{id,name,assignments}`. Clicking a button increments the corresponding `scenes/<i>/applyTrigger` monotonic counter — RuntimeCourier on the Agent side picks the change up and calls `Runtime::applyScene`. The widget itself never calls the runtime directly.

The trigger counter is seeded from the section's current value on subscribe so reconnects don't re-fire the last applied scene (per Phase 17a's persistence note). `lastAppliedScene` drives an "active" highlight on whichever button matches the last successful apply.

Passive on its own — the owner (an activity or container widget) calls `setSection()` to wire it up. Tests construct the section directly to exercise the round trip without a live runtime.