Fix reply line number mismatch with range endLine

Ensure that when creating a reply to a comment that has a range, the
reply's line number is set to the range's end line. This prevents HTTP
400 validation errors from the backend when the parent comment has a
mismatched line and range.

Bug: Google b/530348226
Release-Notes: Fix backend validation error when replying to some comments with ranges.
TAG=agy
CONV=dbd1a853-fed6-4eff-9f7f-e2b143c427c1
Change-Id: Ieebe384b5daad1bf4db166b205042024689e4968

polygerrit-ui/app/utils/comment-util.ts

diff --git a/polygerrit-ui/app/utils/comment-util.ts b/polygerrit-ui/app/utils/comment-util.ts
index 2419783..ef08cf0 100644
--- a/polygerrit-ui/app/utils/comment-util.ts
+++ b/polygerrit-ui/app/utils/comment-util.ts
@@ -202,7 +202,7 @@
     path: replyingTo.path,
     patch_set: replyingTo.patch_set,
     side: replyingTo.side,
-    line: replyingTo.line,
+    line: replyingTo.range ? replyingTo.range.end_line : replyingTo.line,
     range: replyingTo.range,
     parent: replyingTo.parent,
     in_reply_to: replyingTo.id,

polygerrit-ui/app/utils/comment-util_test.ts

diff --git a/polygerrit-ui/app/utils/comment-util_test.ts b/polygerrit-ui/app/utils/comment-util_test.ts
index e8fe606..abda42c 100644
--- a/polygerrit-ui/app/utils/comment-util_test.ts
+++ b/polygerrit-ui/app/utils/comment-util_test.ts
@@ -8,6 +8,7 @@
   computeDisplayLine,
   createCommentThreads,
   createNew,
+  createNewReply,
   createUserFixSuggestion,
   getContentInCommentRange,
   getMentionedThreads,
@@ -748,4 +749,36 @@
       assert.equal(computeDisplayLine({}), '');
     });
   });
+
+  suite('createNewReply', () => {
+    test('standard comment reply (no range)', () => {
+      const replyingTo = {
+        ...createComment(),
+        id: 'parent_id' as UrlEncodedCommentId,
+        line: 5,
+      };
+      const reply = createNewReply(replyingTo, 'reply message', false);
+      assert.equal(reply.line, 5);
+      assert.isUndefined(reply.range);
+      assert.equal(reply.in_reply_to, 'parent_id');
+    });
+
+    test('reply to comment with range (mismatched line)', () => {
+      const replyingTo = {
+        ...createComment(),
+        id: 'parent_id' as UrlEncodedCommentId,
+        line: 1,
+        range: {
+          start_line: 1,
+          start_character: 0,
+          end_line: 2,
+          end_character: 5,
+        },
+      };
+      const reply = createNewReply(replyingTo, 'reply message', false);
+      assert.equal(reply.line, 2); // Should match range.end_line, not replyingTo.line
+      assert.deepEqual(reply.range, replyingTo.range);
+      assert.equal(reply.in_reply_to, 'parent_id');
+    });
+  });
 });