Llama GUI 26.11.0

What's Changed

• Update llama.cpp flag compatibility notes by @thomas9120 in #414
• Improve flag sync smoke timeout diagnostics by @thomas9120 in #415
• Document router memory margin flag decision by @thomas9120 in #416
• Hide retired backends from new installs by @thomas9120 in #418

Full Changelog: v26.10.7...v26.11.0