probe: int8 weight-only compressed-tensors DiT artifact kit (issue 5)

quantize_dit_int8wo.py builds the offline W8A16 artifact (per-channel
symmetric int8, pack-quantized via compressed-tensors' own packer,
per-component config wrapper so encoder/VAE stay BF16, digest manifest);
serve.sh/probe.py/gate.py/psnr.py adapt the issue-2 kit for the
structure-gated capacity matrix (1-4 refs x seeds 2301-2304).

tests/quantization/test_quant_factory.py

@@ -36,10 +36,15 @@ def _int8_weight_only_disk_config() -> dict:
     }
 
 
-def test_hyphenated_registry_method_builds_from_str() -> None:
-    config = _build_single("compressed-tensors")
+def test_hyphenated_registry_method_builds_from_disk_schema() -> None:
+    # A bare str spec cannot construct compressed-tensors (a serialized-format
+    # method with no parameterless default); the serialized schema must build.
+    with pytest.raises(TypeError, match="Cannot instantiate CompressedTensorsConfig"):
+        _build_single("compressed-tensors")
+    disk = _int8_weight_only_disk_config()
+    disk.pop("quant_method")
+    config = _build_single("compressed-tensors", **disk)
     assert isinstance(config, CompressedTensorsConfig)
-    assert config.get_name() == "compressed-tensors"
 
 
 @pytest.mark.parametrize("spelling", ["compressed-tensors", "compressed_tensors"])