test: cover exact module flag diagnostics

[qartik]

Summary

• Add a regression for unsupported dynamic_qubit_management module flag diagnostics.
• Simplify exact module flag diagnostic formatting to the actual multi-value contract used by current validation.

Validation

• cargo test test_validate_qir_reports_exact_expected_dynamic_module_flag_value --all-features
• cargo mutants --package qir-qis --all-features --test-tool cargo --file src/lib.rs --re validate_exact_module_flag
• make lint
• make test

This addresses the latest scheduled Robustness failure from run 25661067525, where cargo-mutants reported one missed mutant in aux::validate_exact_module_flag.

[Copilot]

Pull request overview

This PR improves QIR module-flag validation diagnostics and adds a regression test to ensure unsupported dynamic_qubit_management flag values produce the expected “one of …” diagnostic, addressing a missed cargo-mutants case in aux::validate_exact_module_flag.

Changes:

• Simplified validate_exact_module_flag to always format expected values using the multi-value “one of …” form.
• Added a regression test that feeds an invalidly-typed dynamic_qubit_management module flag value and asserts the exact expected diagnostic text.

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