Improve the `read_file` tool prompt for long files (#34542)

Closes [#ISSUE](https://github.com/zed-industries/zed/issues/31780)

Release Notes:

- Enhanced `read_file` tool call result message for long files.
313f5968ebAdam committed on 7/16/2025, 4:32:58 PM· committed by GitHubparent9ab3d55
1 file changedLine totals unavailable