🎨 Support alias-safe repeated qubit loads

[burgholzer]

🤖 AI text below 🤖

Description

Make repeated and runtime-indexed qubit register loads alias-safe without relying
on CSE for correctness.

The QC-to-QCO conversion now treats qubit memref.load operations as access
provenance. It materializes register-backed qubits immediately around each
quantum operation, commits results in reverse extraction order, and carries
complete QTensor values through structured control flow. Local QTensor
canonicalizations only fold accesses whose indices MLIR proves equal.

The typed OpenQASM frontend now allocates non-scalar qubit declarations as
storage and emits checked point-of-use loads. Quantum register access therefore
no longer expands into width-dependent scf.index_switch dispatch. Exact
duplicate simultaneous operands are rejected semantically, while potentially
aliasing dynamic gate and barrier operands receive runtime assertions.

Fixes #1893

Validation

• Clean LLVM/MLIR 22 release build.
• All 4,404 configured CTest cases pass; two existing QDMI tests remain
  configured as skipped.
• Focused QC, QCO, QTensor, QC-to-QCO, QCO-to-QC, OpenQASM, compiler, and
  round-trip suites pass.
• mqt-cc successfully emits QC, QCO, and Adaptive QIR for dynamic gate,
  modifier, measurement, reset, and barrier accesses.
• All repository lint hooks pass.
• Fresh independent review of the exact published source found no actionable
  issues.

AI assistance

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and preparation of this pull-request description. The commits include
Assisted-by: GPT-5.6 via Codex trailers.

Checklist

• The pull request only contains commits that are focused and relevant to
  this change.
• I have added appropriate tests that cover the new/changed functionality.
• I have updated the documentation to reflect these changes.
• I have added entries to the changelog for any noteworthy additions,
  changes, fixes, or removals.
• I have added migration instructions to the upgrade guide (if needed).
• The changes follow the project's style guidelines and introduce no new
  warnings.
• The changes are fully tested and pass the CI checks.
• I have reviewed my own code changes.

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[codecov]

Codecov Report

❌ Patch coverage is 95.67669% with 23 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...lib/Dialect/QC/Translation/OpenQASMToQCEmitter.cpp	92.0%	10 Missing ⚠️
mlir/lib/Conversion/QCToQCO/QCToQCO.cpp	97.0%	9 Missing ⚠️
mlir/lib/Target/OpenQASM/OpenQASMSemantics.cpp	90.3%	3 Missing ⚠️
mlir/lib/Dialect/QC/Builder/QCProgramBuilder.cpp	92.8%	1 Missing ⚠️

📢 Thoughts on this report? Let us know!

[burgholzer]

Just two small requests for changes. Otherwise, this should be good to go.