fix(github): add pagination tests and fix truncation warning logic

F1: Add comprehensive pagination tests for ListReviews covering:
- Multi-page behaviour (2 full + 1 partial page)
- Exact-multiple-of-pageSize (extra empty-page round-trip)
- maxReviewPages cutoff (cap hit, results still returned)
- Empty first page (PR with no reviews)

F2: Fix truncation warning logic by moving it outside the loop with
a 'truncated' flag. Previously, the warning fired inline at page==maxPages
which could miss the case where the short-page break fires first on the
cap page. Now it only fires when the loop exits because the cap was reached
and the last page was full (indicating more data likely exists).

Also adds SetReviewPagination to Client for test-time override of page
size and max pages, following the existing SetRetryBackoff pattern.

github/reviews.go

@@ -153,11 +153,21 @@ func (c *Client) PostReview(ctx context.Context, owner, repo string, number int,
 // ListReviews retrieves all reviews for a pull request with pagination.
 // GitHub review states are translated to canonical vcs values.
 func (c *Client) ListReviews(ctx context.Context, owner, repo string, number int) ([]vcs.Review, error) {
-	var allReviews []vcs.Review
+	perPage := reviewsPerPage
+	if c.reviewPageSize > 0 {
+		perPage = c.reviewPageSize
+	}
+	maxPages := maxReviewPages
+	if c.reviewMaxPages > 0 {
+		maxPages = c.reviewMaxPages
+	}
 
-	for page := 1; page <= maxReviewPages; page++ {
+	var allReviews []vcs.Review
+	truncated := false
+
+	for page := 1; page <= maxPages; page++ {
 		reqURL := fmt.Sprintf("%s/repos/%s/%s/pulls/%d/reviews?per_page=%d&page=%d",
-			c.baseURL, url.PathEscape(owner), url.PathEscape(repo), number, reviewsPerPage, page)
+			c.baseURL, url.PathEscape(owner), url.PathEscape(repo), number, perPage, page)
 
 		body, err := c.doGet(ctx, reqURL)
 		if err != nil {
@@ -183,17 +193,23 @@ func (c *Client) ListReviews(ctx context.Context, owner, repo string, number int
 			})
 		}
 
-		if len(responses) < reviewsPerPage {
+		if len(responses) < perPage {
 			break
 		}
 
-		if page == maxReviewPages {
-			slog.Warn("ListReviews hit page limit; results may be truncated",
-				"owner", owner, "repo", repo, "pr", number,
-				"maxPages", maxReviewPages, "reviewsFetched", len(allReviews))
+		// If we just fetched page maxPages and it was full (the short-page break
+		// above didn't fire), more reviews likely exist beyond our limit.
+		if page == maxPages {
+			truncated = true
 		}
 	}
 
+	if truncated {
+		slog.Warn("ListReviews hit page limit; results may be truncated",
+			"owner", owner, "repo", repo, "pr", number,
+			"maxPages", maxPages, "reviewsFetched", len(allReviews))
+	}
+
 	return allReviews, nil
 }