New panel design

project_structure.txt

@@ -30,9 +30,35 @@ main/
 │   ├── ui_manager.h
 │   └── ui_manager.c
 └── api/
+    ├── ha_config.h         (entity IDs -- tracked, not secret)
+    ├── ha_template.h       (Jinja template, built from the HA_LIGHT_LIST X-macro)
+    ├── ha_data.h
+    ├── ha_data.c           (parsing + presentation -- SHARED with sim/)
+    ├── ha_client.h
+    ├── ha_client.c         (esp_http_client transport -- device only)
     ├── ambient_weather.h
-    └── ambient_weather.c
+    └── ambient_weather.c   (cloud fallback, used only when HA is unreachable)
+
+sim/                        (desktop simulator -- NOT part of the IDF build)
+├── CMakeLists.txt          (own cmake project; idf.py never looks in here)
+├── lv_conf.h               (host LVGL config; font list must match sdkconfig.defaults)
+├── sim_main.c              (SDL window / headless PNG capture, mock data)
+├── lvgl_port_sim.c         (host implementation of main/ui/lvgl_port.h)
+├── README.md
+├── snapshots/              (captured HA responses, used as render fixtures)
+└── compat/                 (ESP-IDF header stand-ins, so main/ui/*.c compiles as-is)
+    ├── esp_err.h
+    ├── esp_log.h
+    ├── esp_check.h
+    └── esp_compat.c
+
+tools/
+├── ha_discover.py          (list Home Assistant entity IDs; reads $HA_TOKEN)
+└── ha_snapshot.py          (capture HA responses into sim/snapshots/)
 
 Note: main/ subdirectories are plain source folders, not ESP-IDF components.
 IDF only auto-discovers components under a top-level components/ directory,
 so all sources are registered by main/CMakeLists.txt.
+
+The simulator compiles main/ui/ui_manager.c unmodified against desktop LVGL,
+which is why that file must stay free of hardware access. See sim/README.md.