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_jets.py

@@ -62,7 +62,7 @@ class ShiftedJets(unittest.TestCase):
                     level_blocks=list(blocks),level_objects=[(),(),(body(),)],
                     level_jets=[(),(),(jet(),)])
         module.cuda.mem_alloc.assert_not_called()
-        module.compiler.compile_kernel.assert_not_called()
+        module.compiler.build_module.assert_not_called()
 
     def test_switch_upload_only_then_raw_remap_keeps_live_velocity(self):
         run,module,allocations,storage,objects=ready();clone=None