🐛 Traverse reordered while tensors

[burgholzer]

🤖 AI text below 🤖

Summary

• Teach TensorIterator to follow tensor values through scf.while.
• Resolve the actual before-region argument → condition operand → result mapping
  instead of assuming positional identity.
• Support backward traversal from a while result to its corresponding init
  value.
• Add a regression test with reordered classical and tensor values.
• Add this general SCF/QTensor fix to the existing MLIR infrastructure changelog
  entry.

Context

This general SCF/QTensor issue was found while working on loop lowering for the
OpenQASM integration in #1910. It is independent of the frontend and applies to
any pipeline that carries linearly typed quantum tensors through scf.while.

Validation

• QTensor utility tests: 2 passed
• uvx prek run --from-ref origin/main --to-ref HEAD
• git diff --check origin/main...HEAD

[codecov]

Codecov Report

❌ Patch coverage is 76.47059% with 8 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
mlir/lib/Dialect/QTensor/Utils/TensorIterator.cpp	76.4%	8 Missing ⚠️

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