compiler: one build_module/set_params path for all three module owners

Simulation, PeriodicBlockStepper and FixedPatchStepper levels each repeated
generate_config -> compile_kernel -> load_module -> cleanup and the
d_params pack/upload. They now call compiler.build_module(cfg, entry,
arch=..., n_objects=..., block_root_bc=...) and compiler.set_params.
Simulation no longer keeps its build directory alive until close (nothing
read it after loading). Removes the unused compile_kernel_v2 alias.
Host fakes and lifecycle tests follow the new seam; the close-retry case
for build-directory cleanup goes with the removed cleanup step.
No kernel, numerical or launch change.

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

tests/unit/test_shifted_storage.py

@@ -135,7 +135,7 @@ class ShiftedStorage(unittest.TestCase):
             with self.assertRaisesRegex(ValueError,'all-blocked|blocked refined levels below'):
                 module.FixedPatchStepper(cfg,context=None,refinements=[(4,4,20,28)],
                                          level_blocks=blocks)
-        module.compiler.compile_kernel.assert_not_called()
+        module.compiler.build_module.assert_not_called()
 
     def test_uniform_block_codec_and_raw_snapshot(self):
         path = Path(backend.r.__file__).with_name('block_stepper.py')
@@ -151,7 +151,7 @@ class ShiftedStorage(unittest.TestCase):
         cuda.mem_get_info.return_value=(10**9,10**9)
         cuda.mem_alloc.side_effect=lambda size: Mock()
         gpu=Mock();gpu.get_global.return_value=(Mock(),20)
-        compiler.load_module.return_value=gpu
+        compiler.build_module.return_value=gpu
         context=Mock(activate=nullcontext,sm_arch='sm_70')
         layout=module.BlockLayout2D.build(16,16,4,4)
         cfg=replace(backend.CFG,nx=16,ny=16,ddf_shifting=True)