feat: unify Sparo brand and product UI system

[GCWing]

Summary

• Establish a deterministic PNG brand source of truth with generate, sync, and verification commands, then migrate desktop, installer, mobile Web, relay, README, favicon, app icon, tray, mark, and wordmark consumers.
• Add responsive brand primitives, startup and thinking motion, delayed loading treatment, About branding, brand-aware theme tokens, and a complete runtime typography contract across the design system.
• Refine Work Dock and new-Work composition, move thinking visibility into the model selector, simplify Agentic OS header controls, and align localized product styling with the shared visual contract.

Validation

• pnpm run brand:check
• pnpm run type-check:web
• pnpm run build:web:unchecked
• pnpm run build:design-system
• pnpm run build:mobile-web
• pnpm --dir installer run type-check
• cargo check -p sparo-desktop
• git diff --cached --check

Notes

• Web UI and design-system production bundles were built successfully. Native Tauri rendering was not manually exercised in this submission.