fix: protocol 2 core review findings

From the review of #99:
- A sync could stall when a client took a slot the moment another left:
  loop() used up the new client's sync on the old one. The slots move
  to ProtoSlots, a pure module with native tests, and loop() takes a
  slot's wants only for the client it read (takeWants).
- Deleting a group sends its shades, whose inGroup changed. Deleting a
  shade unlinks it from its groups and sends them, so a new shade given
  its id doesn't join them.
- next and sync with an id get an ok reply, and a message in pieces
  gets one bad request, not one per piece.
- Feeds check for loop() before they write the event buffer, and log
  an event too large, as events do.
- editChanges() (ModelEditor, native tests) says what clients get after
  an edit; the edit result carries the shade a group gained or lost.
  order() takes a sort_list_t.
- The frame writers move to ProtoFrame. Renames: pf to proto_field_t,
  the X-macro letters to TYPE/FIELD/ERR/FEED, proto_request_t to
  proto_message_t, REQ_* to WANTS_*, fmt to eventJson. The event
  bodies share sendItem(), the connection type name lives in
  ESPNetwork, and the loop() task check in SocketEmitter.
- e2e: the heap floor check skips when the low since boot is already
  under it; tests for replies to next and sync and a long message.
- SECURITY_PLAN.md splits step 1 into 1a-1d.

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

src/ShadeController.cpp

@@ -287,6 +287,10 @@ bool SomfyShadeController::deleteShade(uint8_t shadeId) {
       this->shades[i].clear();
     }
   }
+  // Its groups lose it, or a new shade given its id would join them.
+  for(uint8_t i = 0; i < SOMFY_MAX_GROUPS; i++) {
+    if(this->groups[i].getGroupId() != 255 && this->groups[i].unlinkShade(shadeId)) this->groups[i].configChanged();
+  }
   this->commit();
   return true;
 }
@@ -298,14 +302,14 @@ bool SomfyShadeController::deleteRoom(uint8_t roomId) {
         if(shades[j].roomId == roomId) {
           shades[j].roomId = 0;
           shades[j].emitState();
-          shades[j].changed |= SHADE_CHANGED_CONFIG;
+          shades[j].configChanged();
         }
       }
       for(uint8_t j = 0; j < SOMFY_MAX_GROUPS; j++) {
         if(groups[j].roomId == roomId) {
           groups[j].roomId = 0;
           groups[j].emitState();
-          groups[j].changed |= GROUP_CHANGED_CONFIG;
+          groups[j].configChanged();
         }
       }
       rooms[i].emitState("roomRemoved");
@@ -319,6 +323,11 @@ bool SomfyShadeController::deleteRoom(uint8_t roomId) {
 bool SomfyShadeController::deleteGroup(uint8_t groupId) {
   for(uint8_t i = 0; i < SOMFY_MAX_GROUPS; i++) {
     if(this->groups[i].getGroupId() == groupId) {
+      // Its shades are no longer in a group, which their inGroup shows.
+      for(uint8_t j = 0; j < SOMFY_MAX_GROUPED_SHADES && groups[i].linkedShades[j] != 0; j++) {
+        SomfyShade *shade = this->getShadeById(groups[i].linkedShades[j]);
+        if(shade) shade->configChanged();
+      }
       groups[i].emitState("groupRemoved");
       protoSocket.groupRemoved(groupId);
       groups[i].unpublish();