text: Assert text anchor offset validity on construction (#38441)

Attempt to aid debugging some utf8 indexing issues

Release Notes:

- N/A

Co-authored-by: Mikayla Maki <mikayla@zed.dev>
a2c71d3d20Lukas Wirth committed on 9/22/2025, 11:20:46 AM· committed by GitHubparent7962045
5 files changedLine totals unavailable