Remove Cursor provider support across server and web

- drop `cursor` from provider/model contracts and runtime validation
- remove Cursor-specific UI options, settings, and model normalization paths
- update server/web tests and fixtures to cover Codex + Claude Code only
040011dbc7Julius Marminge committed on 3/16/2026, 5:35:53 PMparent858116d
26 files changedLine totals unavailable