webui: remember sidebar panels per layout

[edwin-zvs]

Summary:

• default lineage and operator panels to collapsed in narrow mobile layouts
• keep wide desktop defaults expanded
• persist collapse choices independently per responsive layout, with legacy preference fallback
• update the Web UI design spec

Testing:

• cargo build
• cargo test -p construct-daemon web_index_html_serves_dev_with_poller_and_falls_back_to_embedded
• parsed the embedded inline JavaScript with Node
• browser-verified fresh mobile and desktop defaults, independent breakpoint preferences, reload persistence, and zero console errors

[edwin-zvs]

Responsive default verification:

Mobile (390 × 700): lineage and operator start collapsed.

Desktop (1200 × 800): both start expanded.

[edwin-zvs]

Responsive default verification:

Mobile (390 × 700): lineage and operator start collapsed.

Desktop (1200 × 800): both start expanded.

[edwin-zvs]

Responsive default verification:

Mobile (390 × 700): lineage and operator start collapsed.

Desktop (1200 × 800): both start expanded.