🐛 Contain allocation failures in QDMI device C APIs

[denialhaag]

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System and Environment Information

• MQT Core: current main and the 3.9 QDMI device implementation
• QDMI: 1.3.3
• Language: C++20
• Platforms: all supported platforms; the issue is independent of the operating system and compiler

Bug Description

Two allocation-capable entry points in the superconducting QDMI provider can let C++ exceptions escape through the C API:

• MQT_SC_QDMI_device_session_set_parameter calls setDeviceConfigurationParameter, which constructs and assigns strings and filesystem paths.
• MQT_SC_QDMI_device_session_create_device_job allocates a job and inserts it into an unordered_map.

An allocation failure can therefore throw std::bad_alloc instead of returning QDMI_ERROR_OUTOFMEM. Other unexpected exceptions from an entry point can also cross the C boundary instead of returning QDMI_ERROR_FATAL.

The current QDMI-on-IQM implementation needs the same protection. IQM_QDMI_device_session_set_parameter constructs strings, and IQM_QDMI_device_session_create_device_job uses throwing new without an exception barrier.

QMAP inherited this behavior in its neutral-atom provider and contains it in munich-quantum-toolkit/qmap@4bd4c153. That change makes the allocation-capable methods non-throwing, maps std::bad_alloc to QDMI_ERROR_OUTOFMEM, maps other exceptions to QDMI_ERROR_FATAL, and keeps the output job handle null on failure.

Steps to Reproduce

1. Allocate a superconducting QDMI device session.
2. Inject an allocation failure while copying a device configuration parameter, or initialize the session and inject a failure while creating a device job.
3. Call the corresponding exported device function.
4. Observe that std::bad_alloc escapes instead of producing a QDMI status code.

The exported C entry points should contain every exception. They should return QDMI_ERROR_OUTOFMEM for allocation failures, return QDMI_ERROR_FATAL for other unexpected failures, and leave output handles in a documented safe state.