Closes #49957 Also adds `start_of_input` context, and modifies both `{start,end}_of_input` to work for both single line and auto height editor modes. https://github.com/user-attachments/assets/e30f2b20-a96c-49d5-9eb6-3c95a485d14a Before you mark this PR as ready for review, make sure that you have: - [x] Added a solid test coverage and/or screenshots from doing manual testing - [x] Done a self-review taking into account security and performance aspects - [x] Aligned any UI changes with the [UI checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist) Release Notes: - Added support for multi-line search and replace input in Buffer Search and Project Search --------- Co-authored-by: Nathan Sobo <nathan@zed.dev>