fix(ui): show inline rename text in session sidebar

[fibr]

Summary

• apply the live rename editor layout to the session sidebar as well as the vertical tab rail
• prevent the sidebar tab label's ellipsis paint from hiding the focused input
• add a Chromium regression test covering visible, focused sidebar typing

Verification

• npm run test:browser -- test/inline-rename.test.ts (14 passed)
• npm test (316 files passed, 6,185 tests passed)
• npm run typecheck
• npm run lint
• npm run check:frontend-syntax
• npm run check:public-assets
• npm run format:check
• manually verified the rich sidebar in Chromium: typed text and caret render in the focused editor

[fibr]

Hi, just a small enhancement to the sidebar mode -- i can't see what i'm typing in renaming sessions in the sidebar and this should fix it. Hope it can be taken in :-)