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/13-search-cent-rounding/hidden/test_hidden.py

@@ -0,0 +1,10 @@
+import unittest
+from app.fin.tally import consolidate
+
+
+class Hidden(unittest.TestCase):
+    def test_half_up(self):
+        self.assertEqual(float(consolidate([1.005])), 1.01)
+        self.assertEqual(float(consolidate([2.675])), 2.68)
+        self.assertEqual(float(consolidate([1.0, 0.004])), 1.0)
+        self.assertEqual(float(consolidate([0.1, 0.2])), 0.3)