fix: name the file each layer reads in slots.py

Each content-checked line ended with a verdict on the platform's list,
printed at pipeline step 3b. The line now says which emulators read the
other file, and the closing count says the rest follow the platform's
list. The module source carries no such verdict, a test reads it.

tests/test_slots.py

@@ -414,6 +414,9 @@ class TestArbitration(unittest.TestCase):
     def test_the_reported_line_gives_the_ground_for_the_decision(self):
         kept = slots.format_decision(slots.arbitrate(self._conflict(), "md5"))
         self.assertIn("verifies content", kept)
+        # A fact about each layer, no verdict on the platform's list.
+        self.assertIn("the file dolphin reads", kept)
+        self.assertNotIn("wrong", slots.__loader__.get_source("slots").lower())
         served = slots.format_decision(slots.arbitrate(self._conflict(), "existence"))
         self.assertIn("both are satisfied", served)