fix(studio): Properly return complete keymap from RPC (#2696)

Ensure the set active physical layout RPC returns the full keymap
details including the available layers.

app/src/studio/keymap_subsystem.c

@@ -97,23 +97,28 @@ static bool encode_keymap_layers(pb_ostream_t *stream, const pb_field_t *field,
     return true;
 }
 
-zmk_studio_Response get_keymap(const zmk_studio_Request *req) {
-    LOG_DBG("");
-    zmk_keymap_Keymap resp = zmk_keymap_Keymap_init_zero;
+static void populate_keymap_extra_props(zmk_keymap_Keymap *keymap) {
+    keymap->max_layer_name_length = CONFIG_ZMK_KEYMAP_LAYER_NAME_MAX_LEN;
 
-    resp.layers.funcs.encode = encode_keymap_layers;
-
-    resp.max_layer_name_length = CONFIG_ZMK_KEYMAP_LAYER_NAME_MAX_LEN;
-    resp.available_layers = 0;
+    keymap->available_layers = 0;
 
     for (zmk_keymap_layer_index_t index = 0; index < ZMK_KEYMAP_LAYERS_LEN; index++) {
         zmk_keymap_layer_id_t id = zmk_keymap_layer_index_to_id(index);
 
         if (id == UINT8_MAX) {
-            resp.available_layers = ZMK_KEYMAP_LAYERS_LEN - index;
+            keymap->available_layers = ZMK_KEYMAP_LAYERS_LEN - index;
             break;
         }
     }
+}
+
+zmk_studio_Response get_keymap(const zmk_studio_Request *req) {
+    LOG_DBG("");
+    zmk_keymap_Keymap resp = zmk_keymap_Keymap_init_zero;
+
+    resp.layers.funcs.encode = encode_keymap_layers;
+
+    populate_keymap_extra_props(&resp);
 
     return KEYMAP_RESPONSE(get_keymap, resp);
 }
@@ -332,6 +337,7 @@ zmk_studio_Response set_active_physical_layout(const zmk_studio_Request *req) {
         zmk_keymap_SetActivePhysicalLayoutResponse_init_zero;
     resp.which_result = zmk_keymap_SetActivePhysicalLayoutResponse_ok_tag;
     resp.result.ok.layers.funcs.encode = encode_keymap_layers;
+    populate_keymap_extra_props(&resp.result.ok);
 
     if (old == index) {
         return KEYMAP_RESPONSE(set_active_physical_layout, resp);