feat: make the harness backend-agnostic

Everything about which accelerator a run targets was previously spelled CUDA:
device discovery went through nvidia-smi, pinning through CUDA_VISIBLE_DEVICES,
the vendor guard only recognised NVIDIA, and the -p plugin list was hardcoded in
run_pytest.sh with no way to drop the CUDA-only members. Running the same
operator corpus on another vendor's device therefore meant editing the drivers.

The selection now hangs off one ZL_BACKEND variable (cuda/musa/rocm/ascend, with
the usual aliases):

- backends/ owns per-backend device enumeration, visibility env keys and
  capability flags, so nothing above it names a vendor;
- plugin_plan.py derives the -p list from those capabilities instead of a
  hardcoded array, which is what lets a non-CUDA run omit the graph-capture and
  cluster-fix plugins rather than watch them fail;
- _timing_plugin selects the timer from the same capabilities: CUDA keeps
  graph capture with its per-shape fallback, other backends stay on upstream
  do_bench and record timer=direct, because capture-then-fallback on a device
  without graph support only produces noise;
- _device_setup_plugin replaces the NVIDIA-only vendor guard;
- providers/flaggems.py resolves the pytest node, so a caller may pass TEST_NODE
  directly instead of the OP/OP_FILE pair, and SHAPE_MODE=upstream can defer to
  FlagGems' own core_shapes;
- _run_identity.py writes run_identity.json next to each run, recording backend,
  device, timer, autotune mode and the resolved test node. Two runs whose
  calibers differ are otherwise indistinguishable after the fact.

run_batch gains --backend and --devices (--gpus kept as an alias) and carries
backend/device/timer into ops_status.csv. test_backends.py covers the registry,
alias resolution, visibility env and plugin planning.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

batch_summary.py

@@ -39,12 +39,31 @@ DIRECT_NO_CUDAGRAPH_RE = re.compile(r"BENCHMARK_DIRECT_NO_CUDAGRAPH\b")
 REPLAY_FALLBACK_RE = re.compile(r"AUTOTUNE_REPLAY_FALLBACK\b")
 
 SUMMARY_FIELDS = [
-    "repo", "op", "fg_op_name", "dtype", "case_id", "row_status",
+    "repo", "op", "backend", "device", "timer",
+    "fg_op_name", "dtype", "case_id", "row_status",
     "torch_lat", "gems_lat", "speedup", "extra_metrics", "size_detail",
     "op_status", "notes",
 ]
 
 
+def _identity_from_status(status_row: Dict[str, str], op_dir: Path) -> Dict[str, str]:
+    """Backend/device/timer from ops_status.csv, falling back to run_identity.json."""
+    backend = (status_row.get("backend") or "").strip()
+    device = (status_row.get("device") or status_row.get("gpu") or "").strip()
+    timer = (status_row.get("timer") or "").strip()
+    ident_path = op_dir / "run_identity.json"
+    if ident_path.is_file() and not (backend and device and timer):
+        try:
+            from _run_identity import load_identity
+            ident = load_identity(str(op_dir))
+            backend = backend or str(ident.get("backend") or "")
+            device = device or str(ident.get("device") or ident.get("gpu") or "")
+            timer = timer or str(ident.get("timer") or "")
+        except Exception:
+            pass
+    return {"backend": backend, "device": device, "timer": timer}
+
+
 def parse_run_log(text: str) -> List[Dict[str, str]]:
     """把 run.log 里的全部结果表解析为行列表（跨多个 dtype 表）。"""
     rows: List[Dict[str, str]] = []
@@ -133,10 +152,11 @@ def summarize(batch_dir: Path, out_path: Optional[Path] = None) -> Path:
             text = log.read_text(errors="replace")
             status_row = status_by_dir.get(f"{repo}/{op_dir.name}", {})
             op = status_row.get("op") or op_dir.name
+            ident = _identity_from_status(status_row, op_dir)
             table_rows = parse_run_log(text)
             if not table_rows:
                 all_rows.append({
-                    "repo": repo, "op": op, "fg_op_name": "", "dtype": "",
+                    "repo": repo, "op": op, **ident, "fg_op_name": "", "dtype": "",
                     "case_id": "", "row_status": "", "torch_lat": "",
                     "gems_lat": "", "speedup": "", "extra_metrics": "",
                     "size_detail": "",
@@ -150,7 +170,8 @@ def summarize(batch_dir: Path, out_path: Optional[Path] = None) -> Path:
                 idx = case_counter.get(key, 0)
                 case_counter[key] = idx + 1
                 all_rows.append({
-                    "repo": repo, "op": op, "case_id": f"case_{idx:03d}",
+                    "repo": repo, "op": op, **ident,
+                    "case_id": f"case_{idx:03d}",
                     "op_status": status_row.get("status", ""),
                     "notes": status_row.get("notes", ""),
                     **row,