
Copilot rail starters can fill the chat input without sending.

### Added

- Copilot rail **deferred example questions** — `copilot_rail(..., deferred=True)` copies the question into the chat input on click instead of sending it. Per-item override: `{"title", "question", "deferred": True}` (or a `(title, question, deferred)` triple). Starters stay visible until a turn is actually sent.

### Changed

- BI → Semantic (`make bi-semantic`) passes `deferred=True` so starter clicks fill the input for edit-then-send. App Builder still sends on click.

