Fixes#31340
When the attached Open Terminal runs on Windows, the AGENTS.md in its home directory was never handed to the model. The home check only accepted POSIX absolute paths, so a drive-letter or UNC home such as C:\ProgramData\OpenTerminal\inst was treated as invalid and the file was skipped without any log line.
The check now also accepts Windows absolute paths. Relative and drive-relative homes are still skipped, and POSIX homes send byte-identical requests.
The file path keeps its forward-slash join. Open Terminal normalises the path on the host, so C:\Users\bob/AGENTS.md opens C:\Users\bob\AGENTS.md. Picking ntpath.join for Windows homes would give native separators on the wire but adds a second branch for no change in which file gets read.
Verified against Open Terminal's own path resolution with Windows semantics for drive-letter, forward-slash, drive-root, trailing-backslash and UNC homes, over both the backend request and the browser direct-connection path.
