test(D1): read build metadata while the private build directory exists

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

tests/validation/multigrid/test_refinement_followup.py

@@ -271,7 +271,7 @@ class NormalBuildGPU(unittest.TestCase):
                 parts = line.split()
                 if len(parts) == 3 and parts[0] == "#define":
                     definitions[parts[1]] = parts[2]
-            generated.append((metadata["config"], definitions, build))
+            generated.append((metadata["config"], definitions, metadata))
             return build
 
         max_error = max_bc_error = 0.0
@@ -290,8 +290,7 @@ class NormalBuildGPU(unittest.TestCase):
                     self.assertEqual(float(fine_defines[name].removesuffix("f")), 0, name)
                 # The root's physical slot/reservoir walls come from BLOCK_ROOT_BC=1
                 # (module constant d_block_wall); the fine level has none.
-                root_meta = json.loads((Path(generated[0][2])/".celeris-build").read_text())
-                fine_meta = json.loads((Path(generated[1][2])/".celeris-build").read_text())
+                root_meta, fine_meta = generated[0][2], generated[1][2]  # read before cleanup
                 self.assertEqual((root_meta["block_root_bc"], fine_meta["block_root_bc"]), (1, 0))
                 # Independently derive all target links, including the eight
                 # whose coarse sources are uncovered, from physical midpoints.