Perfect responsive navigation and evidence access

[jonashertner]

Outcome

• replaces the overloaded phone layer rail with a compact grouped selector
• gives every map layer its own concise data-status line
• makes the semantic data view readable on phones and gives every river row a unique reach identity
• makes long-page contents compact by default on narrow screens and adds direct keyboard access to the map
• leads the project page with the whole-water-cycle protection mission
• aligns governance with the actual protected-branch process and adds external-link checks to pull requests
• fixes a browser-discovered sticky layer-index overlap at desktop and tablet widths

Validation

• npm run release
• npm run check:links (81 primary links; 0 dead, one transient timeout on a Graubünden page)
• npm audit (0 vulnerabilities)
• Chrome QA at 320×568, 390×844, 768×1024, 1024×768, and 1440×900
• keyboard skip-to-map and mobile data-card interaction checks