[SandObserver]

Summary

• Add placeholder(width, height, radius) to the widget toolbox: a rounded, aria-hidden shape in a theme-aware grey, recoloured on light surfaces through --wt-ph. Its style is injected once on first use.
• Books draws grey spines of varied height, a grey heading bar and grey footer bars until data arrives, and no longer shows "Reading" before it knows the shelf name.
• Now Playing shows the service's band colour and name from its settings and grey bars on the label, instead of "Nothing playing", until it has data.
• The VPN view, Weather, DNS and Pull requests draw grey shapes where their content goes. The DNS legend stays hidden until real data arrives.
• Placeholders are removed by the first render. A widget that never loads keeps them under its error caption.

Testing
All green, Docker build included. Added tests for the placeholder helper and that no widget page states a value before its data arrives.

Changelog

Changed

• Widgets show soft placeholder shapes while they load, and Books and Now Playing no longer show a heading or "Nothing playing" before their data arrives.

Checklist

• Stays within the project constraints: one container, no runtime dependencies, no build step (see CONTRIBUTING.md).
• Tests added or updated for new logic, and the full suite, lint, and typechecks pass.
• Docs updated if behavior or configuration changed.