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/styles.css

@@ -399,6 +399,16 @@ body {
   white-space: nowrap;
 }
 
+/* Overlay shown over a widget disabled via action.widget logic: dims it and
+   blocks interaction while still surfacing the right-click context menu. */
+.widget-disable-overlay {
+  position: absolute;
+  z-index: 10;
+  background: rgba(20, 25, 35, 0.45);
+  cursor: not-allowed;
+  box-sizing: border-box;
+}
+
 /* ── Unknown widget ────────────────────────────────────────────────────────── */
 
 .unknown-widget {
@@ -1361,6 +1371,44 @@ body {
 }
 .flow-localvar-actions .panel-btn { flex: 1; }
 
+/* Repeated rows in inspector editors (export columns, dialog fields). */
+.flow-row-edit {
+  display: flex;
+  align-items: center;
+  gap: 0.35rem;
+  margin-bottom: 0.35rem;
+}
+.flow-row-edit .prop-input { flex: 1; min-width: 0; }
+.flow-row-add {
+  width: 100%;
+  margin-top: 0.15rem;
+}
+
+.flow-field-edit {
+  border: 1px solid #2a3548;
+  border-radius: 4px;
+  padding: 0.4rem;
+  margin-bottom: 0.4rem;
+  display: flex;
+  flex-direction: column;
+  gap: 0.35rem;
+}
+.flow-field-head {
+  display: flex;
+  align-items: center;
+  gap: 0.35rem;
+}
+.flow-field-head .prop-input { flex: 1; min-width: 0; }
+.flow-field-kind {
+  font-size: 0.75rem;
+  color: #94a3b8;
+  flex: 0 0 auto;
+}
+.flow-field-add {
+  display: flex;
+  gap: 0.35rem;
+}
+
 /* ── History pane ───────────────────────────────────────────────────────── */
 
 .history-pane {
@@ -3570,7 +3618,25 @@ kbd {
 
 .logic-dialog-input {
   width: 100%;
-  margin-bottom: 0.75rem;
+  margin-bottom: 0;
+}
+
+/* A single field row (input or display) in a multi-value dialog. */
+.logic-dialog-field {
+  display: flex;
+  flex-direction: column;
+  gap: 0.2rem;
+  margin-bottom: 0.6rem;
+}
+.logic-dialog-label {
+  font-size: 0.8rem;
+  color: #94a3b8;
+}
+.logic-dialog-value {
+  font-size: 0.9rem;
+  font-weight: 600;
+  color: #e2e8f0;
+  padding: 0.2rem 0;
 }
 
 .logic-dialog-actions {