Drop `scrollbar-gutter: stable both-edges` / `stable` from `.scrollbar-thin` and `.scrollbar-thin-edge` so scrollbars overlay content without reserving space, fixing layout inconsistencies between overlay and classic scrollbar environments. Restore padding that was previously reduced to compensate for the gutter: `px-1` to `px-3` in git-log-tab, `px-2` to `px-4` in virtualized-message-thread, and add `px-2` to sidebar-conversation-list and session-files-tab. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>