fix(sysinfo): raise on explicit device with no compatible EP (#431)

[timenick]

Closes #431.

Summary

• winml config --device npu previously logged a warning and exited 0 with an unusable config when no NPU EP (QNN / VitisAI / OpenVINO) was advertised. The failure surfaced later at compile/inference time, far from the misconfiguration.
• resolve_device() now raises ValueError for explicit device requests with no compatible EP. commands/config.py and commands/build.py already route ValueError to click.UsageError → non-zero exit with a clean message naming the missing EPs.
• --device auto is unchanged: it still walks the priority list and falls through to GPU/CPU when an NPU EP is missing (acceptance criterion 3).

Before / after

Before (on a box with NPU silicon but no QNN/VitisAI/OpenVINO):

$ winml config -m microsoft/resnet-50 --device npu --precision int8 -o out.json
WARNING - Device 'npu' requested but no compatible EP found. ...
✅ Config saved to: out.json       ← exit 0, but the config is unusable

After:

$ winml config -m microsoft/resnet-50 --device npu --precision int8 -o out.json
Error: Device 'npu' requested but no compatible EP is available.
Compatible EPs: ['VitisAIExecutionProvider', 'QNNExecutionProvider', 'OpenVINOExecutionProvider'].
Available EPs: ['CPUExecutionProvider', 'DmlExecutionProvider'].
$ echo $?
2