Get Strategy Experiments Lifecycle

Experiments for a strategy, grouped by lifecycle position.

Backs the strategy-info side-panel "Experiments" section. Returns:

• active: at most one — the currently-selected or running experiment.
• backlog: queued/proposed experiments not yet selected.
• completed: terminal states (accepted, rejected, inconclusive, completed, archived, stale). Most recently decided first.

Each entry includes the latest trial summary so the frontend can render a consolidated "completed experiment" card without a second round trip.