Propagate runtime approval and sandbox settings to turn startup

- Add `approvalPolicy` and `sandboxMode` to turn-start command and requested payload contracts
- Pass runtime mode-derived values from `ChatView` when dispatching `thread.turn.start`
- Thread provider options through decider/reactor into session startup, with tests updated
5d64138a27Julius Marminge committed on 2/27/2026, 4:48:18 AMparent4d6e8e1
6 files changedLine totals unavailable