⚡ Avoid redundant target-compilation liveness analysis

[simon1hofmann]

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Description

• Remove the final whole-IR remove-dead-values pass from target compilation; the earlier QCO cleanup already establishes global liveness.
• Keep CSE after native synthesis and keep target-conformance verification last.
• Protect the optimization with an end-to-end fixed-point regression containing a private helper call, dynamic qco.if, and one- and two-qubit synthesis.

Stack

1. ✨ Preserve classical control through target mapping #2179 — classical-control-aware target mapping
2. ⚡ Avoid redundant target-compilation liveness analysis #2180 — target-compilation liveness scaling (this PR)
3. ⚡ Keep wide OpenQASM register conditions linear #2181 — wide OpenQASM register conditions

Testing

• mqt-core-mlir-unittests-compiler: 146 passed.
• uvx nox -s lint and git diff --check: passed on the complete detached stack.

AI assistance: Codex assisted with diagnosis, implementation, review, testing, stack construction, and this description.

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 95.21912% with 24 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
mlir/lib/Dialect/QCO/IR/SCF/IfOp.cpp	94.6%	9 Missing ⚠️
...lir/lib/Dialect/QCO/Transforms/Mapping/Mapping.cpp	93.9%	9 Missing ⚠️
mlir/lib/Compiler/TargetCompilation.cpp	95.6%	6 Missing ⚠️

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