Restore the bundled runtime staging script to upstream so this PR stays focused on the Microsoft Foundry provider and does not carry an unrelated Windows symlink fallback change.
Handle Windows az device-code login, tenant fallback, and Azure resource/deployment discovery so onboard can reuse existing Microsoft Foundry setups without manual endpoint entry. Normalize GPT-5 deployments onto the Foundry responses base URL at selection and runtime auth time, and fall back to hard links for Windows plugin staging so local builds and chats work end-to-end.
