Remove github/review.go and github/identity.go, replacing them with a
consolidated github/reviews.go that:

- Uses doJSONRequest for PostReview and DismissReview (cleaner than
  manual marshal + doRequestWithBody)
- Adds paginated ListReviews with per_page=100 and max 100 pages
- Consolidates GetAuthenticatedUser and userResponse type (previously
  duplicated in identity.go)
- Preserves all sentinel errors (ErrCannotDeleteSubmittedReview,
  ErrConflictingCommitIDs), state translation, commit ID validation,
  and SupersedeReviews

This prevents the redeclaration errors that occur when both review.go
and reviews.go exist in the same package, as described in issue #116.

Closes #116

@@ -0,0 +153,4 @@
+	for page := 1; page <= maxReviewPages; 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)
+

@@ -0,0 +172,4 @@
+			allReviews = append(allReviews, vcs.Review{
+				ID:       r.ID,
+				Body:     r.Body,
+				User:     vcs.UserInfo{Login: r.User.Login},

@@ -2,6 +2,7 @@ package github
 
 import (
 	"context"

@@ -0,0 +156,4 @@
+	if c.reviewMaxPages > 0 {
+		maxPages = c.reviewMaxPages
+	}
+

@@ -2,6 +2,7 @@ package github
 
 import (
 	"context"

@@ -0,0 +218,4 @@
+// (APPROVED, CHANGES_REQUESTED, or COMMENTED per GitHub API naming) returns
+// ErrCannotDeleteSubmittedReview.
+func (c *Client) DeleteReview(ctx context.Context, owner, repo string, number int, reviewID int64) error {
+	reqURL := fmt.Sprintf("%s/repos/%s/%s/pulls/%d/reviews/%d",

@@ -0,0 +168,4 @@
+	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, perPage, page)
+

@@ -0,0 +263,4 @@
+		if err := c.DismissReview(ctx, owner, repo, prNumber, old.ID, "Superseded by new review"); err != nil {
+			errs = append(errs, fmt.Errorf("dismiss review %d: %w", old.ID, err))
+		}
+	}

@@ -194,6 +199,13 @@ func (c *Client) SetRetryBackoff(d []time.Duration) error {
 	return nil

@@ -0,0 +153,4 @@
+// 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) {
+	perPage := reviewsPerPage

@@ -0,0 +173,4 @@
+		if err != nil {
+			return nil, fmt.Errorf("list reviews page %d: %w", page, err)
+		}
+

@@ -194,6 +199,13 @@ func (c *Client) SetRetryBackoff(d []time.Duration) error {
 	return nil