feat: allow updating model/variant mid-session #58
Description
Summary
- Model/variant only apply at session creation today; UI edits after start have no effect.
Request
- Add a supported way to change model/variant for an active session (e.g., PATCH /v1/sessions/{id}).
- Wire the Inspector UI to apply changes to the active session and reflect applied values.
Notes
- Claude uses --model only on spawn; Codex/OpenCode read session.model per turn.
- Ensure any agent-specific constraints are validated server-side.