Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@modelopt/onnx/quantization/graph_utils.py`:
- Around line 1235-1261: The _get_inp_b_k_dim function currently always reads K
from axis -2 which is wrong for Gemm when transB=1; update _get_inp_b_k_dim to
detect transB (default 0 for MatMul) from the node (check for attribute "transB"
on matmul_node) and compute k_axis = -1 if transB > 0 else -2, then use k_axis
when indexing into inp_b.values.shape, inp_b_info.type.tensor_type.shape.dim,
and output_map[inp_b.name].shape so all three fallback paths respect
transposition; also add unit tests that cover Gemm nodes with transB=1 to
prevent regressions.
- Around line 1343-1348: The code adds matmul outputs and second-input Variable
names to model.graph.output without deduplication, which can create duplicate
output names; update the logic (in the block handling matmul_nodes / uses of
matmul_node.outputs[0].name and matmul_node.inputs[1].name) to track
already-added output names (e.g., a set of names) and only call
model.graph.output.extend with onnx.ValueInfoProto for a name if it is not
already present in that set (and add it to the set after extending), ensuring
you still skip Constants by checking isinstance(matmul_node.inputs[1],
Variable).

---

Nitpick comments:
In `@tests/unit/onnx/quantization/test_graph_utils.py`:
- Around line 119-182: Add two unit tests in
tests/unit/onnx/quantization/test_graph_utils.py: one that constructs a Gemm
model with op="Gemm" and attribute transB=1 and asserts _get_inp_b_k_dim on its
node returns the correct K (e.g., when B is constant with shape [..., K, N]
transposed), and a second test that exercises
_exclude_matmuls_by_shape_inference where multiple MatMul/Gemm nodes share the
same inp_b Variable (use calibration_shapes only for "A" and provide an
output_map or runtime-output scenario so the code path that reads K from
runtime-output is used) and assert the expected node id is excluded; reference
helpers _make_matmul_model, _get_matmul_nodes, _get_inp_b_k_dim, and
_exclude_matmuls_by_shape_inference to locate relevant setup and ensure
names/ids match existing tests (e.g., "MatMul_0").