refactor(gitea): address review feedback on PR #90

- position.go: Replace O(n) maxPosition scan with O(1) lookup by
  tracking max position during map construction. Also eliminates
  shadowing of the builtin max identifier (Go 1.21+).
- position.go: Add comment clarifying +++ prefix ordering intent.
- adapter.go: Document diff-fetch tradeoff in PostReview.
- adapter_test.go: Remove extra blank line between test functions.

gitea/adapter.go

@@ -150,7 +150,11 @@ func (a *Adapter) PostReview(ctx context.Context, owner, repo string, number int
 
 	var giteaComments []ReviewComment
 	if len(req.Comments) > 0 {
-		// Fetch diff to build position → line number map
+		// Fetch diff to build position → line number map.
+		// The diff is fetched unconditionally when comments exist. This adds latency
+		// for reviews with inline comments but keeps the implementation simple — caching
+		// the diff across calls would add complexity for minimal gain since PostReview
+		// is called at most once per review cycle.
 		diff, err := a.client.GetPullRequestDiff(ctx, owner, repo, number)
 		if err != nil {
 			return nil, fmt.Errorf("fetch diff for position translation: %w", err)