Add Windows SPTI backend, CI check, platform support complete

- scsi/windows.rs: SCSI_PASS_THROUGH_DIRECT via DeviceIoControl
- Device path normalization (D:, \\.\CdRom0, \\.\D:)
- Windows drive discovery (CdRom0-15 + drive letters)
- CI: cargo check on windows-latest
- Platform table: Linux + macOS + Windows all supported

README.md

@@ -114,7 +114,7 @@ All errors are structured with numeric codes. No user-facing English text — ap
 |----------|--------|---------|
 | Linux | Supported | SG_IO ioctl |
 | macOS | Supported | IOKit SCSITask |
-| Windows | Planned | SPTI |
+| Windows | Supported | SPTI |
 
 ## Contributing