Desktop v0.9.21

CodeBurn Desktop 0.9.21. Ships the 0.9.21 CLI engine bundled, which fixes the 0.9.20 app's slow period switches and missing preserved history against a 0.9.21 cache. Live quota for Gemini, Copilot, and Antigravity with per-provider toggles; the dashboard opens on Today; progressive cold start paints in seconds. Full notes: https://github.com/getagentseal/codeburn/releases/tag/v0.9.21