refactor(web): remove Record<string,string> cast in gitlabPushMrReviews

Now that oldPath/newPath are always plain strings, declare position
directly as DiscussionNotePosition and use a single conditional spread
for the optional oldLine field. Removes the redundant
`as unknown as DiscussionNotePosition` cast.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Gavin Williams

packages/web/src/features/agents/review-agent/nodes/gitlabPushMrReviews.ts

@@ -83,24 +83,22 @@ export const gitlabPushMrReviews = async (
         const newPath = fileDiffReview.filename !== '/dev/null' ? fileDiffReview.filename : resolvedOldPath;
         for (const review of fileDiffReview.reviews) {
             const oldLine = fileContextMap?.get(review.line_end);
-            const position: Record<string, string> = {
+            const position: DiscussionNotePosition = {
                 positionType: 'text',
                 baseSha: base_sha,
                 headSha: head_sha,
                 startSha: start_sha,
                 oldPath,
                 newPath,
                 newLine: String(review.line_end),
+                ...(oldLine !== undefined ? { oldLine: String(oldLine) } : {}),
             };
-            if (oldLine !== undefined) {
-                position['oldLine'] = String(oldLine);
-            }
             try {
                 await gitlabClient.MergeRequestDiscussions.create(
                     projectId,
                     prPayload.number,
                     review.review,
-                    { position: position as unknown as DiscussionNotePosition },
+                    { position },
                 );
             } catch (error) {
                 // Inline comment failed (e.g. line not in diff) — fall back to a general MR note