feat: set generated art as dashboard background

[monobyte]

Summary

• declare the ui.dashboardBackground host capability
• add a Loom action that renders and applies the current piece as the Sero dashboard background
• fit dashboard captures within the host limit without changing their aspect ratio
• encode dashboard captures as JPEG while normal wallpaper exports remain PNG

Verification

• npm run typecheck
• npm test — 25 tests passed
• npm run build

Dependency

Requires companion Sero host PR sero-labs/sero#360.

[socket-security]

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	@​earendil-works/​pi-coding-agent@​0.80.6 ⏵ 0.83.0			+1	+1
	@​earendil-works/​pi-agent-core@​0.80.6 ⏵ 0.83.0	+1		+1	+1
	@​earendil-works/​pi-ai@​0.80.6 ⏵ 0.83.0	-1			+1

View full report

[monobyte]

Updated in 7638456 for the simplified host contract. Dashboard captures now fit within 2560 × 1600 and use JPEG quality 0.85. Normal wallpaper exports still use PNG. Typecheck, all 25 tests, and the production build passed.