Add --verify-data CLI flag, Tensor.data property, parallel DataExecutor

- CLI: --verify-data flag enables Phase 2 data verification (ADR-0020)
- Tensor.data: returns actual numpy values (verify-data) or zeros placeholder
- Tensor.__repr__: shows value summary or data=N/A (placeholder)
- DataExecutor: ThreadPoolExecutor for same-timestamp parallel op execution
- BenchResult.engine: exposes op_log/memory_store for Phase 2 access

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

src/kernbench/cli/main.py

@@ -21,6 +21,10 @@ def build_parser() -> argparse.ArgumentParser:
     runp.add_argument(
         "--device", default=None, help="Target device: 'all' or 'sip:<N>' (default: all)"
     )
+    runp.add_argument(
+        "--verify-data", action="store_true", default=False,
+        help="Enable Phase 2 data verification (ADR-0020)",
+    )
     runp.set_defaults(_handler=cmd_run)
 
     probep = sub.add_parser("probe", help="Probe latency and BW for predefined traffic patterns")
@@ -36,9 +40,11 @@ def build_parser() -> argparse.ArgumentParser:
     return p
 
 
-def engine_factory(topology: object, device: DeviceSelector) -> SimEngine:
+def engine_factory(
+    topology: object, device: DeviceSelector, *, enable_data: bool = False,
+) -> SimEngine:
     topo_obj = getattr(topology, "topology_obj", topology)
-    return GraphEngine(topo_obj)
+    return GraphEngine(topo_obj, enable_data=enable_data)
 
 
 def cmd_web(args) -> int:
@@ -53,8 +59,12 @@ def cmd_run(args) -> int:
     topo = resolve_topology(args.topology)
     bench = resolve_bench(args.bench)
     device = resolve_device(args.device)
+    verify_data = getattr(args, "verify_data", False)
 
-    result = run_bench(topology=topo, bench_fn=bench, device=device, engine_factory=engine_factory)
+    def _factory(topology, device):
+        return engine_factory(topology, device, enable_data=verify_data)
+
+    result = run_bench(topology=topo, bench_fn=bench, device=device, engine_factory=_factory)
 
     topo_obj = getattr(topo, "topology_obj", topo)
     spec = getattr(topo_obj, "spec", None)
@@ -62,6 +72,21 @@ def cmd_run(args) -> int:
         print(format_report(result.traces, title=args.bench, spec=spec))
     print(result.summary_text())
 
+    # Phase 2: data execution (ADR-0020)
+    if verify_data and result.engine is not None:
+        from kernbench.sim_engine.data_executor import DataExecutor
+
+        op_log = result.engine.op_log
+        store = result.engine.memory_store
+        if op_log and store is not None:
+            executor = DataExecutor(op_log, store)
+            executor.run()
+            n_gemm = sum(1 for r in op_log if r.op_kind == "gemm")
+            n_math = sum(1 for r in op_log if r.op_kind == "math")
+            print(f"[data] Phase 2 complete: {len(op_log)} ops ({n_gemm} gemm, {n_math} math)")
+        else:
+            print("[data] No op_log recorded — skipping Phase 2")
+
     return 0 if result.completion.ok else 1