WebUI: per-signal vscale toolbar, active-signal highlighting, zoom fix

- Per-signal, per-plot vertical scale state (sigVScale keyed by plotId:signalKey)
  so the same signal in two plots has fully independent vscale config
- Active signal redrawn on top of all series with 2× line width for clear
  visual identification; badge click toggles selection and opens/closes the
  embedded vscale toolbar (click same badge again to deselect)
- Vscale configurator moved from floating popup to a slim toolbar strip
  anchored inside the plot card, with an × close button
- Trigger dropdown shows one entry per array signal with [0…N-1] label;
  opening it shows an index-picker dialog to choose the element
- Zoom resampling: when server returns no data for a zoomed range, fall
  back to the local circular buffer instead of returning empty arrays

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Client/WebUI/hub.go

@@ -82,9 +82,14 @@ func (c *wsClient) readPump() {
 				case "addSource":
 					label, _ := env["label"].(string)
 					addr, _ := env["addr"].(string)
+					mcastGroup, _ := env["multicastGroup"].(string)
+					dataPortF, _ := env["dataPort"].(float64)
 					if addr != "" {
 						select {
-						case c.hub.commandCh <- hubCmd{op: "wsAddSource", label: label, addr: addr}:
+						case c.hub.commandCh <- hubCmd{
+							op: "wsAddSource", label: label, addr: addr,
+							multicastGroup: mcastGroup, dataPort: int(dataPortF),
+						}:
 						default:
 						}
 					}
@@ -139,11 +144,13 @@ type taggedSample struct {
 type hubCmd struct {
 	op       string // "addSource","removeSource","setSourceState","updateConfig",
 	//                "wsAddSource","wsRemoveSource","wsSaveSources"
-	sourceID string
-	label    string
-	addr     string
-	state    string
-	sigs     []SignalInfo
+	sourceID       string
+	label          string
+	addr           string
+	state          string
+	sigs           []SignalInfo
+	multicastGroup string
+	dataPort       int
 }
 
 // Hub is the central broker between UDP clients and WebSocket clients.
@@ -474,7 +481,9 @@ func (h *Hub) Run() {
 
 			case "wsAddSource":
 				if h.sm != nil {
-					go func(label, addr string) { h.sm.Add(label, addr, "", 0) }(cmd.label, cmd.addr)
+					go func(label, addr, mcastGroup string, dataPort int) {
+						h.sm.Add(label, addr, mcastGroup, dataPort)
+					}(cmd.label, cmd.addr, cmd.multicastGroup, cmd.dataPort)
 				}
 
 			case "wsRemoveSource":
@@ -718,9 +727,10 @@ func (h *Hub) buildDataMessageForSource(src *sourceHubState, batch []DataSample)
 			decimT, decimV := lttbDecimate(allT, allV, maxPushPoints)
 			out[pfx+sig.Name] = sigData{T: decimT, V: decimV}
 
-		case n > 1 && sig.TimeMode == TimeModeFullArray:
-			// The time signal has the same N elements as the data signal.
+		case sig.TimeMode == TimeModeFullArray:
 			// Each element pair (timeSig[k], dataSig[k]) is one (t, v) sample.
+			// This handles both standard N-element FullArray signals and
+			// Accumulate-mode scalars (n=1) auto-assigned FullArray time mode.
 			hasTimeSig := sig.TimeSignalIdx != NoTimeSignal && int(sig.TimeSignalIdx) < len(sigs)
 			var timeSigName string
 			timerToSec := 1e-6
@@ -918,7 +928,9 @@ func (h *Hub) buildBinaryDataMessageForSource(src *sourceHubState, batch []DataS
 			decimT, decimV := lttbDecimate(allT, allV, maxPushPoints)
 			pairs[sig.Name] = pairBuf{t: decimT, v: decimV}
 
-		case n > 1 && sig.TimeMode == TimeModeFullArray:
+		case sig.TimeMode == TimeModeFullArray:
+			// Handles both standard N-element FullArray signals and
+			// Accumulate-mode scalars (n=1) with auto-assigned FullArray time mode.
 			hasTimeSig := sig.TimeSignalIdx != NoTimeSignal && int(sig.TimeSignalIdx) < len(sigs)
 			var timeSigName string
 			timerToSec := 1e-6
@@ -957,9 +969,11 @@ func (h *Hub) buildBinaryDataMessageForSource(src *sourceHubState, batch []DataS
 					allV = append(allV, vals[k])
 				}
 			}
-			ringT, ringV := lttbDecimate(allT, allV, maxRingPoints)
-			if rb := h.getRing(pfx + sig.Name); rb != nil {
-				rb.write(ringT, ringV)
+			if writeRing {
+				ringT, ringV := lttbDecimate(allT, allV, maxRingPoints)
+				if rb := h.getRing(pfx + sig.Name); rb != nil {
+					rb.write(ringT, ringV)
+				}
 			}
 			decimT, decimV := lttbDecimate(allT, allV, maxPushPoints)
 			pairs[sig.Name] = pairBuf{t: decimT, v: decimV}