fix(ui): center inactive right drawer tabs

[avabbbb]

Summary

• Put display: inline-flex on every compact right-drawer tab, so inactive and active icons share the same centering behavior.
• Keep the three-icon group centered independently of the trailing collapse button.
• Keep the collapse button on the right in icon-only mode.

Browser evidence

• Mounted the app with the repository CLI on a dynamically assigned loopback port and Playwright Chrome for Testing.
• At a 320 px drawer width, checked the default state and each of the three selected states: group-center offset 0 px; each icon-to-button-center offset 0 px; no console errors.
• Screenshot: .tmp/ui-audit/after/right-agent-tabs.png (local evidence, not committed).

Hosted checks

• CI, Security, FlovartBench: pass.