Preserve StatePreparation width in inverse (backport #16431)

[mergify]

Summary

Fixes #16430.

StatePreparation.inverse() rebuilt integer-bitmap gates from the stored integer alone.
When the original gate was constructed with an explicit num_qubits, that width was lost and the inverse gate fell back to the minimal width implied by the integer value.

For example, StatePreparation(1, num_qubits=2).inverse() returned a 1-qubit gate instead of preserving the original 2-qubit basis-state preparation semantics.

This change forwards the original width for integer-bitmap inputs when rebuilding the inverse gate.

Details

• preserve self.num_qubits in StatePreparation.inverse() for integer inputs
• add a regression covering StatePreparation(1, num_qubits=2).inverse()
• add a regression showing the integer-bitmap inverse and equivalent vector-form inverse both uncompute the same prepared 2-qubit state back to |00>
• add a release note for the public bugfix

Testing

• python -m unittest test.python.circuit.library.test_state_preparation.TestStatePreparation.test_inverse_preserves_integer_bitmap_width test.python.circuit.library.test_state_preparation.TestStatePreparation.test_inverse_integer_bitmap_matches_vector_form
• python -m unittest test.python.circuit.library.test_state_preparation
• python -m ruff check qiskit/circuit/library/data_preparation/state_preparation.py test/python/circuit/library/test_state_preparation.py

Release Notes

• I have added a release note for end user visible changes.

AI usage

• I used AI tooling to help draft and validate this change.
• Tool: Codex (GPT-5)

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This is an automatic backport of pull request #16431 done by [Mergify](https://mergify.com).

[coveralls]

Coverage Report for CI Build 30440730829

Coverage decreased (-0.02%) to 87.637%

Details

• Coverage decreased (-0.02%) from the base build.
• Patch coverage: 2 of 2 lines across 1 file are fully covered (100%).
• 26 coverage regressions across 4 files.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

26 previously-covered lines in 4 files lost coverage.

File	Lines Losing Coverage	Coverage
crates/qasm2/src/parse.rs	12	97.15%
crates/circuit/src/parameter/symbol_expr.rs	8	73.98%
crates/qasm2/src/lex.rs	5	92.29%
crates/qasm2/src/expr.rs	1	93.88%

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Coverage Stats

Relevant Lines:	128768
Covered Lines:	112849
Line Coverage:	87.64%
Coverage Strength:	998368.32 hits per line

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💛 - Coveralls