test(hardware): add comprehensive bus type inference testing

[jra3]

Summary

This PR adds comprehensive testing for hardware bus type inference functions to address issue #161. The implementation follows a four-phase approach covering all device patterns, drivers, and real-world cloud provider scenarios.

What Changed

New Test File

• internal/hardware/graph/bus_inference_test.go (715 lines)
  • 17 test functions covering all four phases
  • 100+ individual test cases
  • Comprehensive device pattern coverage

Test Coverage by Phase

Phase 1: Core Disk Bus Type Pattern Tests

• NVMe Patterns: Base devices, partitions, multiple namespaces (nvme0n1, nvme1n2p1)
• SATA/SCSI Patterns: All device names including extended (sda-sdz, sdaa, etc.)
• IDE Patterns: Legacy disk controllers (hda, hdb, hdc, hdd)
• VirtIO Patterns: KVM/QEMU (vda, vdb) and Xen (xvda, xvdb) virtual disks
• Unknown Patterns: Loop devices, device mapper, MD RAID, eMMC, network block, optical drives
• Edge Cases: Case sensitivity, substring matching, empty strings

Phase 2: Network Driver Detection Tests

• Virtual Interfaces: Loopback, bridge, VLAN, bonding
• VirtIO Drivers: virtio_net, virtio_pci variants
• USB Drivers: Drivers with "usb" in name (usbnet, usb_ethernet)
  • Documents limitation: r8152, asix, ax88179 not detected (no "usb" substring)
• PCI Drivers: Intel (e1000, igb, ixgbe, i40e, ice), Broadcom, Realtek, Mellanox, AWS ENA, VMware vmxnet3, wireless (iwlwifi, ath9k)

Phase 3: Bus Connection Relationship Tests

• All Bus Type Enums: PCI, PCIe, USB, SATA, NVMe, SAS, IDE, SCSI, VirtIO, Unknown
• Bus Address Formatting: PCI addresses (0000:00:1f.2), USB locations (1-1.2)
• Relationship Validation: Proper subject/object/predicate structure
• Protobuf Verification: Successful unmarshaling of ConnectedTo predicates

Phase 4: Real-World Device Pattern Validation

• AWS EC2: NVMe EBS volumes, instance store, Xen paravirtual (xvda)
• GCP: Persistent disks (sda), local NVMe SSDs
• Azure: Managed disks (sda), premium NVMe
• VMware: Paravirtual SCSI (sda), IDE (hda)
• Container Environments: Loop devices, device mapper
• Cloud Network Adapters: AWS ENA, GCP VirtIO, Azure Mellanox, VMware vmxnet3
• Physical Servers: Large disk arrays (27+ disks), mixed NVMe/SATA configurations

Test Statistics

• 17 test functions organized by phase
• 100+ individual test cases covering all scenarios
• All device patterns from issue test: Improve bus type inference testing coverage #161 implemented
• All bus types validated with enum mapping
• Cloud providers (AWS, GCP, Azure, VMware) comprehensively covered

Test Results

Coverage Improvement:

• Before: 70.9%
• After: 75.1%
• Improvement: +4.2 percentage points ✅

All tests passing:

ok      github.com/antimetal/agent/internal/hardware/graph     13.869s coverage: 75.1% of statements

Key Findings

The tests document current implementation behavior:

• ✅ Comprehensive device pattern detection (NVMe, SATA, IDE, VirtIO)
• ✅ Virtual interface detection working correctly
• ✅ VirtIO driver detection working correctly
• ⚠️ USB driver detection limitation: Only detects drivers with "usb" substring
  • Drivers like r8152, asix, ax88179 default to PCI
  • Tests document this as current behavior vs ideal behavior

Success Criteria Met

✅ Achieve comprehensive coverage for bus inference functions
✅ Test all documented device naming patterns
✅ Cover all supported bus types
✅ Validate unknown device fallback behavior
✅ Test relationship creation for all bus types

Testing

# Run all tests
go test ./internal/hardware/graph/...

# Run with coverage
go test ./internal/hardware/graph/... -cover

# Run specific bus inference tests
go test ./internal/hardware/graph/... -run "Infer|BusInference"

Closes #161