- B (left sidebar, 260px): project header, Build pills (Code/Layouts/Infra),
app list, file tree embedded below active app
- D (center): AgentMode as primary content; sessions shown as a horizontal
chip strip at the top instead of a 220px left sidebar
- Right (460px): FileViewer — shows file selected in B's tree / code changes
- F (bottom): Terminal collapsible strip unchanged
- Split CodeContent into FileTree + FileViewer components; lifted file
selection state to BuildHubInner so B and Right share it
Made-with: Cursor