Add widget-control logic action and multi-column CSV / multi-field dialogs

Extend the panel logic editor with two capabilities:

- action.widget: drive a panel widget by id from a flow — enable/disable,
  show/hide, and (for plot widgets) clear, pause, or resume the live plot.
  Wired via a per-widget command store consumed by a Canvas WidgetView wrapper
  (disable overlay / hide) and PlotWidget (pause/clear), reset on panel unmount.
- action.export now emits multiple named arrays as CSV columns with per-column
  labels and an alignment mode (common/any/interpolate); dialogs support asking
  for and displaying multiple values per dialog.

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

web/src/Canvas.tsx

@@ -1,7 +1,8 @@
-import { h } from 'preact';
+import { h, Fragment } from 'preact';
 import { useState, useEffect } from 'preact/hooks';
 import { initLocalState } from './lib/localstate';
 import { logicEngine } from './lib/logic';
+import { getWidgetCmdStore, type WidgetCmd } from './lib/widgetCommands';
 import type { Interface, Widget, SignalRef } from './lib/types';
 import TextView from './widgets/TextView';
 import TextLabel from './widgets/TextLabel';
@@ -42,6 +43,32 @@ interface CtxState {
   signal: SignalRef | null;
 }
 
+// Wraps a single view-mode widget so panel logic (action.widget) can drive it:
+// `hidden` removes it from the view, `disabled` dims it and blocks interaction
+// via a transparent overlay (which still surfaces the right-click menu). Plot
+// pause/clear are handled inside PlotWidget itself.
+function WidgetView({ widget, children, onContextMenu }: {
+  widget: Widget;
+  children: any;
+  onContextMenu: (e: MouseEvent) => void;
+  key?: string;
+}) {
+  const [cmd, setCmd] = useState<WidgetCmd>(() => getWidgetCmdStore(widget.id).get());
+  useEffect(() => getWidgetCmdStore(widget.id).subscribe(setCmd), [widget.id]);
+  if (cmd.hidden) return null;
+  if (!cmd.disabled) return children;
+  return (
+    <Fragment>
+      {children}
+      <div
+        class="widget-disable-overlay"
+        style={`left:${widget.x}px;top:${widget.y}px;width:${widget.w}px;height:${widget.h}px;`}
+        onContextMenu={onContextMenu}
+      />
+    </Fragment>
+  );
+}
+
 interface Props {
   iface: Interface | null;
   onNavigate?: (interfaceId: string) => void;
@@ -131,9 +158,8 @@ export default function Canvas({ iface, onNavigate, timeRange }: Props) {
       <div class="canvas-area" style={`width:${iface.w}px;height:${iface.h}px;`}>
         {iface.widgets.map(widget => {
           const Comp = COMPONENTS[widget.type];
-          return Comp
+          const inner = Comp
             ? <Comp
-                key={widget.id}
                 widget={widget}
                 onContextMenu={(e: MouseEvent) => onCtxMenu(e, widget)}
                 onNavigate={onNavigate}
@@ -141,7 +167,6 @@ export default function Canvas({ iface, onNavigate, timeRange }: Props) {
               />
             : (
               <div
-                key={widget.id}
                 class="unknown-widget"
                 style={`left:${widget.x}px;top:${widget.y}px;width:${widget.w}px;height:${widget.h}px;`}
                 title={`Unknown widget type: ${widget.type}`}
@@ -150,6 +175,15 @@ export default function Canvas({ iface, onNavigate, timeRange }: Props) {
                 <span class="unknown-label">{widget.type}</span>
               </div>
             );
+          return (
+            <WidgetView
+              key={widget.id}
+              widget={widget}
+              onContextMenu={(e: MouseEvent) => onCtxMenu(e, widget)}
+            >
+              {inner}
+            </WidgetView>
+          );
         })}
       </div>