chore: replace toolbar icons — footprints for trace, tap for tap config

- Toggle tracing: "T" → 👣 (footprints — trace = following the path)
- Configure tap: ✎ (pencil) → 🚰 (water tap — tap = intercept the flow)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/components/ProcessDiagram/NodeToolbar.tsx

@@ -16,8 +16,8 @@ interface NodeToolbarProps {
 
 const ACTIONS: { icon: string; action: NodeAction; title: string }[] = [
   { icon: '\uD83D\uDD0D', action: 'inspect', title: 'Inspect' },
-  { icon: 'T', action: 'toggle-trace', title: 'Toggle tracing' },
-  { icon: '\u270E', action: 'configure-tap', title: 'Configure tap' },
+  { icon: '\uD83D\uDC63', action: 'toggle-trace', title: 'Toggle tracing' },
+  { icon: '\uD83D\uDEB0', action: 'configure-tap', title: 'Configure tap' },
   { icon: '\u22EF', action: 'copy-id', title: 'Copy ID' },
 ];