CanvasForge 0.6.0-beta.4

Beta update for testing the AUR update flow.\n\nChanged:\n- Clipboard base64 handoff now saves and copies JPEG instead of PNG for Grok.\n- JPEG handoff scales longest side to 1440px and encodes at quality 88.\n- Clipboard text is data:image/jpeg;base64,... and clipboard MIME is image/jpeg.