[codex] Apply Pencil desktop design

[spaceshipmike]

Summary

• Applies the Pencil-inspired desktop app redesign across the main Projects view, sidebar, and project detail surfaces.
• Rebuilds the home filter bar with responsive wrapping, multi-area filtering, area rail arrow scrolling, hidden rail scrollbar, and a wired + Area creation flow.
• Updates the app mark in the sidebar, aligns control typography/carets, and refreshes the generated Electron renderer bundle.

Validation

• npm run build -w packages/app
• Electron area rail smoke: verified arrow scrolling moves the area chip rail left and right.
• Electron responsive viewport check: verified the home filter bar at 1440, 1280, 1100, 980, and 860 widths with no horizontal overflow or clipped controls.