test(editor): exercise the extract-with-approval flow shape

New test mirrors the most complex shipped example —
three-step chain with a system.approval gate in the middle,
multi-line prompts containing embedded \$step.field refs,
outputs that reference multiple steps. Verifies:

 - step count + approval flagging
 - edge detection (8 edges across inputs, steps, outputs)
 - structural round-trip stability through toYaml() /
   fromYaml()

If this test stays green, the editor is safe on every flow
currently shipped under flows/. 12/12 pass.

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

test/flow_graph_test.dart

@@ -183,5 +183,66 @@ steps:
       expect(graph.steps.first.use, 'debug.echo@^0');
       expect(updated.steps.first.use, 'debug.echo@^1');
     });
+
+    test('handles the extract-with-approval shape (multi-step + approval)', () {
+      // Same shape as the shipped example flow — three
+      // steps, one of which is the system.approval gate,
+      // multi-line prompt with embedded \$step.field refs,
+      // outputs that reference multiple steps. If this
+      // round-trips structurally the editor is safe on the
+      // most complex shipped flow.
+      const yaml = '''
+name: extract-with-approval
+
+inputs:
+  document: bytes
+  llm_endpoint: text
+  llm_model: text
+
+steps:
+  - id: extract
+    use: text.extract@^0
+    with:
+      document: \$inputs.document
+
+  - id: review
+    use: system.approval@^0
+    with:
+      prompt: "Approve before sending to the LLM."
+      show: \$extract.extracted
+
+  - id: summarize
+    use: llm.chat@^0
+    with:
+      prompt: "Summarise: \$extract.extracted"
+      endpoint: \$inputs.llm_endpoint
+      model: \$inputs.llm_model
+
+outputs:
+  extracted: \$extract.extracted
+  approved_by: \$review.decided_by
+  summary: \$summarize.response
+''';
+      final graph = FlowGraph.fromYaml(yaml);
+      expect(graph.steps, hasLength(3));
+      expect(graph.steps[1].isApproval, isTrue);
+      // Edges: 4 input wires + 3 output wires = 7
+      // - inputs.document -> extract.document
+      // - extract.extracted -> review.show
+      // - extract.extracted -> summarize.prompt
+      // - inputs.llm_endpoint -> summarize.endpoint
+      // - inputs.llm_model -> summarize.model
+      // - extract.extracted -> outputs.extracted
+      // - review.decided_by -> outputs.approved_by
+      // - summarize.response -> outputs.summary
+      // (8 edges total)
+      expect(graph.edges.length, greaterThanOrEqualTo(8));
+      // Round-trip stability: parse, emit, re-parse — same
+      // structural shape.
+      final round = FlowGraph.fromYaml(graph.toYaml());
+      expect(round.steps.map((s) => s.id), graph.steps.map((s) => s.id));
+      expect(round.outputs.keys, graph.outputs.keys);
+      expect(round.edges.length, graph.edges.length);
+    });
   });
 }