Function assignReviewers

assignReviewers(
    provider: ReviewerProvider,
    request: RequestReference,
    reviewers: Identity[],
): Promise<AssignmentResult>
Explicitly request reviews, preserving existing assignments. Revalidates eligibility and re-reads assignment state after ambiguous writes.
Parameters
- provider: ReviewerProvider
  Provider with write-capable credentials.
- request: RequestReference
  Repository and PR number/MR IID.
- reviewers: Identity[]
  Provider-qualified identities, normally from suggestion results.
Returns Promise<AssignmentResult>
Assigned, already assigned, and failed identities; no automatic removals.

Throws
ReviewerError For closed/draft requests, invalid identities, or missing essential context.

Remarks
Provider APIs cannot guarantee atomicity against concurrent external edits.
- Defined in src/service.ts:180