refactor: centralize compact date formatting

tests/test_preservation_slice_market.py

@@ -146,6 +146,7 @@ class MarketSliceSourceEquivalenceTests(unittest.TestCase):
             self.assertEqual(sha256(ORIGINAL_ROOT / original), sha256(APP_ROOT / migrated))
         original_tushare = top_level_definitions(ORIGINAL_ROOT / "tushare_client.py")
         original_tushare.pop("_number")
+        original_tushare.pop("_display_date")
         self.assertEqual(
             original_tushare,
             top_level_definitions(APP_ROOT / "backend/data/providers/tushare_client.py"),
@@ -155,6 +156,13 @@ class MarketSliceSourceEquivalenceTests(unittest.TestCase):
             function_contract(APP_ROOT / "backend/data/numbers.py", "finite_number"),
         )
         self.assertIs(canonical_tushare._number, finite_number)
+        self.assertEqual(
+            function_contract(ORIGINAL_ROOT / "tushare_client.py", "_display_date"),
+            function_contract(
+                APP_ROOT / "backend/bootstrap/config.py", "display_compact_date"
+            ),
+        )
+        self.assertIs(canonical_tushare._display_date, bootstrap_config.display_compact_date)
         original_charts = top_level_definitions(ORIGINAL_ROOT / "chart_data_provider.py")
         original_charts.pop("_stock_market_code")
         self.assertEqual(

tests/test_preservation_slice_screener.py

@@ -9,6 +9,7 @@ import advanced_strategies
 import llm_strategy
 import screener
 import strategy_tracking
+from backend.bootstrap import config as bootstrap_config
 from backend.data.numbers import finite_number
 from backend.features.screener import compiler, engine, strategies, tracking
 from backend.features.screener import service as screener_service
@@ -151,12 +152,12 @@ class ScreenerSliceSourceEquivalenceTests(unittest.TestCase):
         self.assertEqual(
             module_contract(
                 ORIGINAL_ROOT / "screener.py",
-                excluded_definitions={"_number"},
+                excluded_definitions={"_display_date", "_number"},
                 exclude_imports=True,
             ),
             module_contract(
                 APP_ROOT / "backend" / "features" / "screener" / "engine.py",
-                excluded_definitions={"_number"},
+                excluded_definitions={"_display_date", "_number"},
                 exclude_imports=True,
             ),
         )
@@ -165,6 +166,13 @@ class ScreenerSliceSourceEquivalenceTests(unittest.TestCase):
             function_contract(APP_ROOT / "backend/data/numbers.py", "finite_number"),
         )
         self.assertIs(engine._number, finite_number)
+        self.assertEqual(
+            function_contract(ORIGINAL_ROOT / "screener.py", "_display_date"),
+            function_contract(
+                APP_ROOT / "backend/bootstrap/config.py", "display_compact_date"
+            ),
+        )
+        self.assertIs(engine._display_date, bootstrap_config.display_compact_date)
         self.assertEqual(
             class_methods(
                 ORIGINAL_ROOT / "backend" / "features" / "screener" / "tracking.py",