agent: Multiline review comments (#47448)

Multiline review comments. Also changes a few existing review comment
types to use anchors instead of absolute offsets

Release Notes:

- N/A
8273e6d868Cameron Mcloughlin committed on 1/23/2026, 6:25:42 AM· committed by GitHubparent7ba0bda
9 files changedLine totals unavailable