Improve sidebar document title space

apps/web/src/navigation.css+12 −1

apps/web/src/theme.test.ts+1 −1

docs/superpowers/plans/2026-08-24-sidebar-document-title-layout.md+144 −0

docs/superpowers/specs/2026-08-24-sidebar-document-title-layout-design.md+3 −3

e2e/document-navigation.e2e.ts+49 −0