Improve dashboard master config and separate slave deadzone updates.

Always show master deadzone input with read/set controls; apply bulk slave
changes via slaves_only without changing the master's BMA456.

Co-authored-by: Cursor <cursoragent@cursor.com>

goTool/api_serve.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"encoding/json"
+	"fmt"
 	"net/http"
 	"strconv"
 
@@ -21,6 +22,8 @@ type deadzoneAPIRequest struct {
 	Deadzone   uint32 `json:"deadzone"`
 	ClientID   uint32 `json:"client_id"`
 	AllClients bool   `json:"all_clients"`
+	// SlavesOnly: with all_clients, push to ESP-NOW slaves only (master BMA456 unchanged).
+	SlavesOnly bool `json:"slaves_only"`
 }
 
 type unicastAPIRequest struct {
@@ -84,12 +87,30 @@ func serveDeadzonePost(w http.ResponseWriter, r *http.Request, link *managedSeri
 		writeJSON(w, http.StatusBadRequest, deadzoneAPIResponse{Error: "invalid JSON"})
 		return
 	}
-	resp, err := link.AccelDeadzone(&pb.AccelDeadzoneRequest{
+	if body.AllClients && body.SlavesOnly {
+		updated, err := applyDeadzoneToSlaves(link, body.Deadzone)
+		if err != nil {
+			writeJSON(w, http.StatusServiceUnavailable, deadzoneAPIResponse{
+				Error: err.Error(),
+			})
+			return
+		}
+		writeJSON(w, http.StatusOK, deadzoneAPIResponse{
+			Deadzone:      body.Deadzone,
+			Success:       updated > 0,
+			SlavesUpdated: updated,
+		})
+		return
+	}
+
+	req := &pb.AccelDeadzoneRequest{
 		Write:      true,
 		Deadzone:   body.Deadzone,
 		ClientId:   body.ClientID,
 		AllClients: body.AllClients,
-	})
+	}
+	// client_id 0 without all_clients: master BMA456 only (same as CLI -client 0).
+	resp, err := link.AccelDeadzone(req)
 	if err != nil {
 		writeJSON(w, http.StatusServiceUnavailable, deadzoneAPIResponse{
 			ClientID: body.ClientID,
@@ -105,6 +126,36 @@ func serveDeadzonePost(w http.ResponseWriter, r *http.Request, link *managedSeri
 	})
 }
 
+// applyDeadzoneToSlaves sets deadzone on each registered slave via per-client UART/ESP-NOW.
+// Does not change the master's local BMA456 (use client_id 0 for that).
+func applyDeadzoneToSlaves(link *managedSerial, deadzone uint32) (uint32, error) {
+	clients, err := link.listClients()
+	if err != nil {
+		return 0, err
+	}
+	var updated uint32
+	for _, c := range clients {
+		resp, err := link.AccelDeadzone(&pb.AccelDeadzoneRequest{
+			Write:    true,
+			Deadzone: deadzone,
+			ClientId: c.GetId(),
+		})
+		if err != nil {
+			continue
+		}
+		if resp.GetSuccess() {
+			updated++
+		}
+	}
+	if len(clients) == 0 {
+		return 0, fmt.Errorf("no slaves registered")
+	}
+	if updated == 0 {
+		return 0, fmt.Errorf("deadzone not applied to any slave")
+	}
+	return updated, nil
+}
+
 func serveUnicastTest(w http.ResponseWriter, r *http.Request, link *managedSerial) {
 	var body unicastAPIRequest
 	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {