[xiaoh-amd (xiaoh-amd)]

Summary
Stop the transpose optimizer from pushing a Transpose through an op when that move does not actually cancel a later Transpose.

Stock ORT treats “any downstream Transpose” as a reason to push. Two Transposes cancel only when their perms are inverses (both disappear). They merge when the perms compose into a remaining Transpose. For a shared Transpose, a merge does not remove the original node, so the graph is not simpler and QDQ layout can be broken.

Behavior
Cost model: waive the cost of a Transpose inserted on the output only if a downstream Transpose would cancel the pushed perm, or the incoming Transpose has a single consumer (merge still drops a node). A shared Transpose that would only merge is not pushed.

QDQ guard: if a Transpose already sits in a complete DQ → Transpose → Q unit, do not push it through that Q unless the relocated Transpose would cancel downstream. Dead-end branches (no Transpose) are allowed when cancellation happens on another branch, because the relocated Transpose can stay on those branches.

Test plan
TestSliceSharedTransposeCancel / TestSliceSharedTransposeNoCancel / TestSliceUnsharedTransposeNoCancel
TestQDQSharedTransposeSliceCancel / TestQDQSharedTransposeSliceNoCancel
TestQDQTransposeNotPushedThroughOwnQ
TransposeOptimizerTests (171 tests) pass on the v1.27.0 build.

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