feat(skill-learning): add surrogate tool evaluator

app-instance/backend/tests/unit/test_skill_learning_surrogate.py

@@ -0,0 +1,31 @@
+from __future__ import annotations
+
+import asyncio
+
+from beaver.skills.learning.surrogate import SurrogateToolEvaluator
+
+
+def test_surrogate_scores_complete_candidate_higher_than_missing_baseline() -> None:
+    evaluator = SurrogateToolEvaluator()
+    baseline = {
+        "arm": "baseline",
+        "tool_calls": [
+            {"tool_name": "mcp_outlook_send_email", "mode": "surrogate", "arguments": {"to": "", "subject": ""}},
+        ],
+    }
+    candidate = {
+        "arm": "candidate",
+        "tool_calls": [
+            {
+                "tool_name": "mcp_outlook_send_email",
+                "mode": "surrogate",
+                "arguments": {"to": "ada@example.com", "subject": "Status", "body": "Done"},
+            },
+        ],
+    }
+
+    result = asyncio.run(evaluator.evaluate(task_text="Send a status email to Ada.", baseline=baseline, candidate=candidate))
+
+    assert result["candidate_score"] > result["baseline_score"]
+    assert result["surrogate_tool_count"] == 2
+    assert result["confidence"] in {"low", "medium"}