When tabbing into the text field of a slider, the text is not preselected

Example: https://0x53a.github.io/UAS-SigVer/

(Source at https://github.com/0x53A/UAS-SigVer/)

When I click into the text field of a slider, the text is automatically selected and I can start typing.

If I instead tab-navigate into the text field of a slider, the text is NOT selected. Instead the cursor is placed at the end.

This means, ``tab -> `` doesn't work, instead a user needs to do ``tab -> CTRL+A -> ``

Reproduce the behavior using the linked UAS-SigVer example, comparing mouse focus with tab navigation into the slider's text field. Trace the egui slider text-field focus handling and verify that tabbing selects the existing text so typing replaces it without requiring Ctrl+A.

Written by the indexing model from the issue text.