OSS-first docs
These docs teach the open system first: contracts, generated surfaces, runtimes, governance, and incremental adoption. Studio shows up as the operating layer on top, not as the source of truth.
Assigns (or reassigns) a review to a reviewer. Idempotent on `(id, assigneeId)` — re-assigning to the same reviewer is a no-op success.
Per SEAMS §1.3 (S-11), emits one `audit.event.append` with kind `review.assigned` (retention class `operational`). Per SEAMS §3.6.4, downstream notifications to the new assignee are fire-and-forget; failure does NOT roll back the assignment.
Capability: `review.act`. Idempotency: required.