Add reverse path response latency for PE DMA and PE_CPU→M_CPU

Model fabric response hop latency for PE-internal operations:
- HBM_CTRL sends PeDmaMsg response on reverse path instead of direct done signal
- PE_CPU sends ResponseMsg via NOC→M_CPU on kernel completion
- Add NOC→PE_DMA and PE_CPU→NOC edges in topology builder
- Make HBM BW test assertions dynamic based on topology efficiency

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/kernbench/components/impls/hbm_ctrl.py

@@ -79,6 +79,14 @@ class HbmCtrlComponent(ComponentBase):
         from kernbench.runtime_api.kernel import MemoryReadMsg, PeDmaMsg
 
         if isinstance(txn.request, PeDmaMsg):
+            reverse_path = list(reversed(txn.path))
+            if len(reverse_path) >= 2:
+                resp_txn = Transaction(
+                    request=txn.request, path=reverse_path, step=0,
+                    nbytes=0, done=txn.done, is_response=True,
+                )
+                yield self.out_ports[reverse_path[1]].put(resp_txn.advance())
+                return
             txn.done.succeed()
             return