[jamesmulcahy]

Summary

This PR adds a button mode that tells the panel to open an entity's page when a physical button is pressed. It's the first step towards "physical button shortcuts", where a button opens a device's page or runs an action. The first user is a small mode that opens the first media player in the panel's room.

This PR only changes the manager ↔ panel interface. Nothing sends the new mode yet, and the change is additive.

Changes

• NSPanelConfig.NSPanelButtonMode.OPEN_ENTITY_PAGE = 5: on press, the panel opens the entity page for the button's topic itself, without a round trip to the manager. The relay is left alone.
• NSPanelConfig.button1_entity_page_topic = 47 and button2_entity_page_topic = 48: the state topic of the entity whose page the button opens. Empty for every other mode.

The panel only needs the state topic: EntityPage::show() already takes one, and every manager entity has get_mqtt_state_topic(). So the same mode will work for lights, thermostats and media players. The manager decides which entity to send.

Compatibility

• Older firmware that receives mode 5 falls into the default: branch of its button handler. It logs "Unknown button action" and does nothing.
• Newer firmware paired with an older manager never receives mode 5.

Generated code comes from docker/protobuf/regenerate.sh. Only protobuf_nspanel changes.

Follow-ups

1. Manager and web UI: a button mode, "Open the room's first media player" (stored as 6), sent as OPEN_ENTITY_PAGE with the first media player in the panel's room, in entities-page order. A room with no media player falls back to NOTIFY_MANAGER. The topic follows the room's entities: every change to them already reloads the manager, which resends each panel's config. Add a button mode that opens the room's first media player #425, with manager and Django tests.
2. Firmware: handle OPEN_ENTITY_PAGE. The page opens from the page-transition task, waking the screen from the screensaver. A press with the page already showing does nothing, and one with another entity's page showing switches entity. Buttons: open an entity page when the manager configures it NSPanelManager-firmware#64, which depends on the media player firmware PR (Media player support NSPanelManager-firmware#27).
3. Later: an entity picker, so a button can open any light, thermostat or media player page, or toggle/activate entities that have no page.

All three pieces have been run together against the dev stack and a QEMU-emulated panel.

I'm opening this as a draft, to get feedback on the message design before the follow-ups build on it.

🤖 Generated with Claude Code