test(benchmarks): add concept-search tasks

Three tasks whose target code shares no vocabulary with the prompt, run in a
repository with generated distractor modules.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

scripts/benchmarks/tasks/11-search-expired-evaluation/hidden/test_hidden.py

@@ -0,0 +1,14 @@
+import unittest
+from datetime import date
+from app.accounts import Account
+from app.ledger.archive import render_period_summary
+
+
+class Hidden(unittest.TestCase):
+    def test_expired_evaluation_blocked(self):
+        with self.assertRaises(PermissionError):
+            render_period_summary(Account('evaluation', date(2026, 1, 1)), '2026-01', today=date(2026, 2, 1))
+
+    def test_running_evaluation_and_paid_allowed(self):
+        self.assertIsInstance(render_period_summary(Account('evaluation', date(2026, 3, 1)), '2026-01', today=date(2026, 2, 1)), bytes)
+        self.assertIsInstance(render_period_summary(Account('paid'), '2026-01', today=date(2026, 2, 1)), bytes)