feat(editor): five distinct type colours + wired/total badge in step header

Two operator-visible improvements:

 - Five payload types now get five distinct hues that
   survive both light and dark themes:
     text   → blue (0xFF42A5F5)
     bytes  → deep orange (0xFFFF7043)
     json   → purple (0xFFAB47BC)
     file   → green (0xFF66BB6A)
     number → amber (0xFFFFCA28)
   Previously bytes + file shared a colour and the palette
   collapsed under custom theme plugins. Hardcoded hues
   keep them readable everywhere.

 - Step headers now carry a small "wired/total" badge.
   When all with-fields carry a `$src.field` reference,
   the badge collapses to a green check icon — the visual
   "this module is fully wired" signal Stefan asked for.
   Partial-wiring shows e.g. "3/5" in a pill matching the
   step accent. Endpoint nodes don't render the badge
   (ratio doesn't apply there).

Computed live from graph.edges + step.with_ values, so the
indicator updates the moment an operator drags a
connection in or out.

Version 0.5.0 -> 0.5.1.

Signed-off-by: flemming-it <sf@flemming.it>

lib/src/widgets/flow_canvas.dart

@@ -311,6 +311,14 @@ class _FlowCanvasState extends State<FlowCanvas> {
     final selected = widget.controller.selectedStepId == step.id;
     final raw = widget.controller.stepStatuses[step.id] ?? StepRunStatus.idle;
     final status = _toNodeStatus(raw);
+    // How many with-fields carry a wired-up `$src.field`
+    // expression. Drives the header's "n/total" badge so the
+    // operator can see at a glance whether the module is
+    // fully connected.
+    final wired = step.with_.values
+        .whereType<Object>()
+        .where((v) => _isWiredExpression(v.toString()))
+        .length;
     return Positioned(
       left: pos.x,
       top: pos.y,
@@ -319,6 +327,7 @@ class _FlowCanvasState extends State<FlowCanvas> {
         title: step.id,
         subtitle: step.use,
         inputPortLabels: step.with_.keys.toList(),
+        wiredCount: wired,
         kind: kindForStep(step),
         selected: selected,
         status: status,
@@ -591,20 +600,26 @@ class _FlowCanvasState extends State<FlowCanvas> {
   }
 
   Color _typeAccent(String type, ThemeData theme) {
-    final cs = theme.colorScheme;
+    // Five distinct hues for the five payload types F-Delta-I
+    // flows declare today. Picked from a high-contrast set
+    // that survives both light and dark themes; intentionally
+    // NOT pulled exclusively from the theme's primary /
+    // secondary / tertiary slots because those collide once
+    // a custom theme plugin is active.
     switch (type) {
       case 'text':
-        return cs.primary;
+        return const Color(0xFF42A5F5); // blue
       case 'bytes':
-      case 'file':
-        return cs.tertiary;
+        return const Color(0xFFFF7043); // deep orange
       case 'json':
-        return cs.secondary;
+        return const Color(0xFFAB47BC); // purple
+      case 'file':
+        return const Color(0xFF66BB6A); // green
       case 'number':
       case 'integer':
-        return Colors.amber.shade400;
+        return const Color(0xFFFFCA28); // amber
       default:
-        return cs.onSurfaceVariant;
+        return theme.colorScheme.onSurfaceVariant;
     }
   }
 
@@ -786,7 +801,6 @@ class _FlowCanvasState extends State<FlowCanvas> {
     return (best - portCenter).distance < 0.5;
   }
 
-
   void _finalizeDraft() {
     final draft = _draft;
     setState(() => _draft = null);