Prepare canary 0.0.21 so installed 0.0.20 builds can receive the merged Agentation integration (#209) and desktop sizing fixes (#211). This increments only the desktop bundle version; the signed release workflow will validate and publish the exact merged revision. Related: #7.

Validation: frozen-lockfile install, package formatting, and diff checks pass. Release CI runs the complete type, formatting, and lint checks before signing and notarization.

### Built in Ace

The version edit, checks, and GitHub operations ran through the real `canary-0-0-21` Ace channel terminal. Codex coordinated the work through an external harness because Ace cannot host that harness yet (#9). A managed clean checkout preserves the pre-existing native recovery backup (#173).