feat: add basic GPU fallback detection when ROCm is not installed

[simonCatBot]

Summary

When ROCm (rocm-smi/rocminfo) is not available, this feature now attempts to gather GPU information via sysfs and lspci. This provides basic GPU metrics without requiring ROCm drivers.

New Features

New endpoint option:

When is set:

• ROCm available → uses ROCm (full detailed metrics)
• ROCm not available + includeBasicGpu=true → uses sysfs/lspci (basic metrics)
• includeBasicGpu=false or omitted → uses systeminformation (limited)

Metrics Provided (Basic Mode)

When using the basic sysfs/lspci fallback:

• GPU name (from VBIOS version string or PCI ID mapping)
• Current/max clock speeds (SCLK, MCLK via pp_dpm_sclk/mclk)
• VRAM total/used (from mem_info_vram_*)
• GPU utilization % (from gpu_busy_percent)
• Temperature (via hwmon when available)
• Driver name
• PCI link width/speed

New Response Field

gpuDetectionMethod - indicates which detection was used:

• rocm - full ROCm detection
• basic-sysfs - sysfs/lspci fallback
• systeminfo - systeminformation fallback
• none - no GPU detected

Files Changed

• src/lib/system/gpu-fallback.ts - New module for basic GPU detection
• src/app/api/system/metrics/route.ts - Updated to use fallback detection with includeBasicGpu option
• tests/unit/gpu-fallback.test.ts - Unit tests for the new module

Testing

All 824 unit tests pass including the 6 new tests for gpu-fallback.ts:

✓ tests/unit/gpu-fallback.test.ts > gpu-fallback > detectBasicGPU > should return empty array when no GPUs detected
✓ tests/unit/gpu-fallback.test.ts > gpu-fallback > detectBasicGPU > should detect AMD GPU from lspci
✓ tests/unit/gpu-fallback.test.ts > gpu-fallback > detectBasicGPU > should parse SCLK states correctly
✓ tests/unit/gpu-fallback.test.ts > gpu-fallback > detectBasicGPU > should handle lspci without VGA entries
✓ tests/unit/gpu-fallback.test.ts > gpu-fallback > hasGPU > should return false when no GPU is detected
✓ tests/unit/gpu-fallback.test.ts > gpu-fallback > hasGPU > should return an array from detectBasicGPU